Clocking Wizard v5.1 LogiCORE IP Product Guide (PG065)

Clocking Wizard v5.1 LogiCORE IP Product Guide (PG065)
Clocking Wizard v5.1
LogiCORE IP Product Guide
Vivado Design Suite
PG065 April 1, 2015
Table of Contents
IP Facts
Chapter 1: Overview
About the Core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recommended Design Experience . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Feature Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Licensing and Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Chapter 2: Product Specification
Performance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Resource Utilization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Port Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Chapter 3: Designing with the Core
General Design Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Clocking. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Resets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Functional Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Core Architecture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Chapter 4: Design Flow Steps
Customizing and Generating the Core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Constraining the Core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Synthesis and Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22
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Chapter 5: Detailed Example Design
Directory and File Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Example Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
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Chapter 6: Test Bench
Appendix A: Verification, Compliance, and Interoperability
Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Hardware Testing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Appendix B: Migrating
Migrating to the Vivado Design Suite. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Differences between the Clocking Wizard and the Legacy DCM and PLL Wizards . . . . . . . . . . . . . 50
Upgrading in the Vivado Design Suite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Appendix C: Debugging
Finding Help on Xilinx.com . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Debug Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Hardware Debug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Appendix D: Additional Resources and Legal Notices
Xilinx Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Please Read: Important Legal Notices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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3
IP Facts
Introduction
LogiCORE IP Facts Table
The LogiCORE™ IP Clocking Wizard core
simplifies the creation of HDL source code
wrappers for clock circuits customized to your
clocking requirements. The wizard guides you
in setting the appropriate attributes for your
clocking primitive, and allows you to override
any wizard-calculated parameter. In addition to
providing an HDL wrapper for implementing
the desired clocking circuit, the Clocking
Wizard also delivers a timing parameter
summary generated by the Xilinx timing tools
for the circuit.
Core Specifics
Supported
Device Family (1)
UltraScale™ Architecture, Zynq®-7000,
7 Series
Supported User
Interfaces
AXI4-Lite
Resources
Special Features
•
Design Files
Verilog and VHDL
Example Design
Verilog and VHDL
Test Bench
Verilog and VHDL
Simulation
Model
•
•
Selection of mixed-mode clock manager
(MMCM)/phase-locked loop (PLL)
primitives. GUI options are enabled for the
supported features for the primitives.
Safe Clock Startup feature enables stable
and valid clock at the output. Enabling
Sequencing provides sequenced output
clocks.
Provides AXI4-Lite interface for dynamically
reconfiguring the clocking primitives for
Multiply, Divide, Phase, or Duty Cycle.
•
Automatically configures clocking primitive
based on user-selected clocking features.
•
Automatically calculates Voltage Controlled
Oscillator (VCO) frequency for primitives
with an oscillator, and provides multiply
and divide values based on input and
output frequency requirements.
Clocking Wizard v5.1
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.xdc (Xilinx Design Constraints)
For supported simulators, see the Xilinx
Design Tools: Release Notes Guide.
Instantiation
Template
Verilog and VHDL Wrapper
Supported
S/W Driver
Not Applicable
Tested Design Flows
Design Entry
Tools
Simulation
Synthesis Tools
Accepts up to two input clocks and up to
seven output clocks per clock network.
•
PLL(E2/E3), MMCM(E2/E3),
Spread Spectrum Clocking
Provided with Core
Constraints File
Features
See Table 2-2.
Vivado® Design Suite
Mentor Graphics Questa®SIM, Vivado
Simulator
Synplify PRO E-2012.03, Vivado Synthesis
Support
Provided by Xilinx @ www.xilinx.com/support
Notes:
1. For a complete listing of supported devices, see the Vivado
IP Catalog.
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Product Specification
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IP Facts
Features (continued)
•
Automatically implements overall configuration that supports phase shift and duty cycle
requirements.
•
Supports Spread Spectrum clocking for MMCM(E2/E3) and allows users to select valid range of
modulation frequency, mode and input/output clocks.
•
Optionally buffers clock signals.
•
Provides the ability to override the selected clock primitive and any calculated attribute.
•
Provides timing estimates for the clock circuit and Xilinx® Power Estimator (XPE) parameters.
•
Provides a synthesizable example design including the clocking network and a simulation test
bench.
•
Provides optional ports for the selected primitive.
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Product Specification
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Chapter 1
Overview
This chapter introduces the Clocking Wizard core and provides related information,
including recommended design experience, additional resources, technical support, and
ways of submitting feedback to Xilinx. The Clocking Wizard core generates source Register
Transfer Level (RTL) code to implement a clocking network matched to your requirements.
Both Verilog and VHDL design environments are supported.
About the Core
The Clocking Wizard is a Xilinx IP core that can be generated using the Xilinx Vivado design
tools, included with the latest Vivado release in the Xilinx ® Download Center.
The core is licensed under the terms of the Xilinx End User License and no FLEX license key
is required.
Recommended Design Experience
The Clocking Wizard is designed for users with any level of experience. Using the wizard
automates the process of creating your clocking network and is highly recommended. The
wizard guides users to the proper primitive configuration and allows advanced users to
override and manually set any attribute. Although the Clocking Wizard provides a fully
verified clocking network, understanding the Xilinx clocking primitives will aid you in
making design trade-off decisions.
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Chapter 1: Overview
Feature Summary
Clocking features include:
•
Frequency synthesis. This feature allows output clocks to have different frequencies
than the active input clock.
•
Spread Spectrum. This feature provides modulated output clocks which reduces the
spectral density of the electromagnetic interference (EMI) generated by electronic
devices. This feature is available for only MMCM(E2/E3)_ADV primitive. UNISIM
simulation support for this feature is not available in current release.
•
Phase alignment. This feature allows the output clock to be phase locked to a
reference, such as the input clock pin for a device.
•
Minimize power. This features minimizes the amount of power needed for the
primitive at the possible expense of frequency, phase offset, or duty cycle accuracy.
•
Dynamic phase shift. This feature allows you to change the phase relationship on the
output clocks.
•
Dynamic reconfiguration. This feature allows you to change the programming of the
primitive after device configuration. When this option is chosen, AXI4-Lite interface is
selected by default for reconfiguring clocking primitive.
•
Balanced. Selecting Balanced results in the software choosing the correct BANDWIDTH
for jitter optimization.
•
Minimize output jitter. This feature minimizes the jitter on the output clocks, but at
the expense of power and possibly output clock phase error. This feature is not
available with 'Maximize input jitter filtering'.
•
Maximize input jitter filtering. This feature allows for larger input jitter on the input
clocks, but can negatively impact the jitter on the output clocks. This feature is not
available with 'Minimize output jitter'.
•
Safe Clock Startup and Sequencing. This feature is useful to get stable and valid clock
at the output. It also enables Clocks in a particular sequence order as specified in the
configuration.
Applications
•
Creation of clock network having required frequency, phase and duty cycle with
reduced jitter
•
Electromagnetic Interference reduction in electronic devices using Spread Spectrum
feature
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Chapter 1: Overview
Licensing and Ordering Information
This Xilinx LogiCORE™ IP module is provided at no additional cost with the Xilinx Vivado™
Design Suite under the terms of the Xilinx End User License. Information about this and
other Xilinx LogiCORE IP modules is available at the Xilinx Intellectual Property page. For
information about pricing and availability of other Xilinx LogiCORE IP modules and tools,
contact your local Xilinx sales representative.
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Chapter 2
Product Specification
Clocking Wizard helps create the clocking circuit for the required output clock frequency,
phase and duty cycle using mixed-mode clock manager (MMCM)(E2/E3) or phase-locked
loop (PLL)(E2/E3) primitive. It also helps verify the output generated clock frequency in
simulation, providing a synthesizable example design which can be tested on the hardware.
It also supports Spread Spectrum feature which is helpful in reducing Electromagnetic
interference. Figure 2-1 shows a block diagram of the Clocking Wizard.
X-Ref Target - Figure 2-1
$EMONSTRATION4EST"ENCH
%XAMPLE$ESIGN
0ROVIDED#LOCKING.ETWORK
/PTIONAL
#LOCK
'ENERATORS
)NPUT
#LOCKS
"UFS
&REQUENCY
#HECK
/PTIONAL&EEDBACK
/PTIONAL
#ONFIGURED
#LOCKING
0RIMITIVE
"UFS
/UTPUT
#LOCKS
#OUNTER
!RRAY
(IGH
"ITS
8
Figure 2-1:
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Chapter 2: Product Specification
Performance
Maximum Frequencies
Table 2-1 shows the maximum frequencies for Virtex®-7 devices. The maximum
frequencies are same for MMCM and PLL.
Table 2-1:
Maximum Frequency Virtex-7 Devices
Clock
Speed Grade
-1
-2
-3
Input
800 MHz
933 MHz
1066 MHz
Output
800 MHz
933 MHz
1066 MHz
S_AXI_ACLK
250 MHz
250 MHz
250 MHz
Table 2-2 shows the minimum frequencies of MMCM in Virtex®-7 devices.
Table 2-2:
Minimum Frequency of MMCM in Virtex-7 Devices
Clock
Speed Grade
-1
-2
-3
Input
10
10
10
Output
10
10
10
Table 2-3 shows the minimum frequencies of PLL in Virtex®-7 devices.
Table 2-3:
Minimum Frequency of PLL in Virtex-7 Devices
Clock
Speed Grade
-1
-2
-3
Input
19
19
19
Output
19
19
19
Power
•
Minimize power feature minimizes the amount of power needed for the primitive at the
possible expense of frequency, phase offset, or duty cycle accuracy.
•
Power Down input pin when asserted, places the clocking primitive into low power
state, which stops the output clocks.
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Chapter 2: Product Specification
Resource Utilization
Resource utilization is available in the Clocking Wizard GUI by clicking the Resource tab.
This does not include AXI4-Lite resources when Dynamic Reconfiguration is enabled. Refer
to Dynamic Reconfiguration through AXI4-Lite for more information.
X-Ref Target - Figure 2-2
Figure 2-2:
Resource Tab
Port Descriptions
Table 2-4 describes the input and output ports provided from the clocking network. All
ports are optional, with the exception being that at least one input and one output clock are
required. The options selected determine which ports are actually available to be
configured. For example, when Dynamic Reconfiguration is selected, these ports are
exposed. Any port that is not exposed is appropriately tied off or connected to a signal
labeled unused in the delivered source code.
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Chapter 2: Product Specification
Table 2-4:
Clocking Wizard I/O
Port (5)
I/O
Description
Input Clock Ports
(1)
clk_in1
Input
Clock in 1 : Single-ended primary input clock port.
Available when single-ended primary clock source
is selected.
clk_in1_p
Input
Clock in 1 Positive and Negative: Differential
primary input clock port pair. Available when a
differential primary clock source is selected.
clk_in2 (2)
Input
Clock in 2: Single-ended secondary input clock
port. Available when a single-ended secondary
clock source is selected.
clk_in2_p (2)
Input
Clock in 2 Positive and Negative: Differential
secondary input clock port pair. Available when a
differential secondary clock source is selected.
clk_in_sel (2)
Input
Clock in Select: When ’1’, selects the primary input
clock; When ’0’, the secondary input clock is
selected. Available when two input clocks are
specified.
clkfb_in
Input
Clock Feedback in: Single-ended feedback in port
of the clocking primitive. Available when
user-controlled on-chip, user controller-off chip, or
automatic control off-chip feedback option is
selected.
clkfb_in_p
Input
clkfb_in_n
Input
Clock Feedback in: Positive and Negative:
Differential feedback in port of the clocking
primitive. Available when the automatic control
off-chip feedback and differential feedback option
is selected.
clk_in1_n
clk_in2_n (2)
Output Clock Ports
clk_out1
Output
Clock Out 1: Output clock of the clocking network.
clk_out1 is not optional.
clk_out1_ce
Input
Clock Enable: Chip enable pin of the output buffer.
Available when BUFGCE or BUFHCE or BUFR buffers
are used as output clock drivers.
clk_out1_clr
Input
Counter reset for divided clock output: Available
when BUFR buffer is used as output clock driver.
clk_out2_n (3)
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Output
Clock Out 2 - n: Optional output clocks of the
clocking network that are user-specified. For an
MMCM, up to seven are available. For UltraScale
PLLE3, up to two clocks are available and for 7
series/Zynq-7000PLLE2, up to six clocks are
available
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Chapter 2: Product Specification
Table 2-4:
Clocking Wizard I/O (Cont’d)
Port (5)
I/O
Description
clk_out[2-n]_ce (3)
Input
Clock Enable: Chip enable pin of the output buffer.
Available when BUFGCE or BUFHCE or BUFR buffers
are used as output clock drivers.
clk_out[2-n]_clr (3)
Input
Counter reset for divided clock output: Available
when BUFR buffer is used as output clock driver.
clkfb_out
Output
Clock Feedback Out: Single ended feedback port
of the clocking primitive. Available when the
user-controlled feedback or automatic control off
chip with single ended feedback option is selected.
clkfb_out_p
Output
clkfb_out_n
Output
Clock Feedback Out: Positive and Negative:
Differential feedback output port of the clocking
primitive. Available when the user-controlled
off-chip feedback and differential feedback option
is selected.
Dynamic Reconfiguration Ports
daddr[6:0]
Input
Dynamic Reconfiguration Address: Address port
for use in dynamic reconfiguration; active when den
is asserted
dclk
Input
Dynamic Reconfiguration Clock: Clock port for
use in dynamic reconfiguration
den
Input
Dynamic Reconfiguration Enable: Starts a
dynamic reconfiguration transaction. Refer to DRP
protocol details for more information.
di[15:0]
Input
Dynamic Reconfiguration Data in: Input data for
a dynamic reconfiguration write transaction; active
when den is asserted
do[15:0]
Output
Dynamic Reconfiguration Data Out: Output data
for a dynamic reconfiguration read transaction;
active when drdy is asserted
drdy
Output
Dynamic Reconfiguration Ready: Completes a
dynamic reconfiguration transaction
dwe
Input
Dynamic Reconfiguration Write Enable: When
asserted, indicates that the dynamic
reconfiguration transaction is a write; active when
den is asserted
Dynamic Phase Shift Ports (2)
psclk
Input
Dynamic Phase Shift Clock: Clock for use in
dynamic phase shifting
psen
Input
Dynamic Phase Shift Enable: Starts a dynamic
phase shift transaction
psincdec
Input
Dynamic Phase Shift increment/decrement:
When ’1’; increments the phase shift of the output
clock, when ’0’, decrements the phase shift
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Chapter 2: Product Specification
Table 2-4:
Clocking Wizard I/O (Cont’d)
Port (5)
psdone
I/O
Description
Output
Dynamic Phase Shift Done: Completes a dynamic
phase shift transaction
Status and Control Ports (4)
reset/resetn
Input
Reset (Active High)/Resetn (Active Low): When
asserted, asynchronously clears the internal state of
the primitive, and causes the primitive to re-initiate
the locking sequence when released
power_down
Input
Power Down: When asserted, places the clocking
primitive into low power state, which stops the
output clocks
input_clk_ stopped
Output
Input Clock Stopped: When asserted, indicates
that the selected input clock is no longer toggling
locked
Output
Locked: When asserted, indicates that the output
clocks are stable and usable by downstream
circuitry
cddcreq (6)
cddcdone (6)
Input
Clock Divide Dynamic Change (CDDC) request. This
is asserted after last DRP request is performed and
then de-asserted after last DRDY
Output
Clock Divide Dynamic Change (CDDC) done. When
output counters are updated this signal is asserted
s_axi_aclk
Input
AXI Clock
s_axi_aresetn
Input
AXI Reset, Active-Low
Input
AXI Write address. The write address bus gives the
address of the write transaction.
Input
Write address valid. This signal indicates that a valid
write address and control information are available.
Output
Write address ready. This signal indicates that the
slave is ready to accept an address and associated
control signals.
s_axi_awaddr[10:0]
s_axi_awvalid
s_axi_awready
s_axi_wdata[31:0]
s_axi_wstb[3:0]
s_axi_wvalid
s_axi_wready
Input
Write data
Input
Write strobes. This signal indicates which byte lanes
to update in memory.
Input
Write valid. This signal indicates that valid write
data and strobes are available.
Output
Write ready. This signal indicates that the slave can
accept the write data.
Output
Write response. This signal indicates the status of
the write transaction
00 = OKAY (normal response)
10 = SLVERR (error condition)
11 = DECERR (not issued by core)
s_axi_bresp[1:0]
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Chapter 2: Product Specification
Table 2-4:
Clocking Wizard I/O (Cont’d)
Port (5)
s_axi_bvalid
s_axi_bready
s_axi_araddr[10:0]
I/O
Output
s_axi_rdata[31:0]
Response ready. This signal indicates that the
master can accept the response information.
Input
Read address. The read address bus gives the
address of a read transaction.
Input
Read address valid. This signal indicates, when High,
that the read address and control information is
valid and remains stable until the address
acknowledgement signal, s_axi_arready, is High.
Output
Read address ready. This signal indicates that the
slave is ready to accept an address and associated
control signals.
Output
Read data
Output
Read response. This signal indicates the status of
the read transfer.
00 = OKAY (normal response)
10 =SLVERR (error condition)
11 = DECERR (not issued by core)
Output
Read valid. This signal indicates that the required
read data is available and the read transfer can
complete.
s_axi_rresp[1:0]
s_axi_rvalid
s_axi_rready
s_axis_aclk
Write response valid. This signal indicates that a
valid write response is available.
Input
s_axi_arvalid
s_axi_arready
Description
Input
Read ready. This signal indicates that the master can
accept the read data and response information.
Input
The global clock signal. All streaming signals from
Read interface of the FIFO are sampled on the rising
edge of s_axis_aclk.
Notes:
1. At least one input clock is required; any design has at least a clk_in1 or a clk_in1_p/clk_in1_n port.
2. Not available when primitive chosen is UltraScale PLL or Spread Spectrum is selected for MMCM.
3. The clk_out3 and clk_out4 ports are not available when Spread Spectrum is selected.
4. Exposure of every status and control port is individually selectable.
5. This version of clocking wizard supports naming of ports as per requirements. The list mentioned in Table 2-4 is the default
port list.
6. Ports used for dynamic change of output counter without reset. Available only in MMCME3 primitive.
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Chapter 3
Designing with the Core
This chapter includes guidelines and additional information to make designing with the
core easier.
General Design Guidelines
•
Provide the available input clock information for Frequency and Jitter.
•
If the same input clock is used by other logic in the design then provide No buffer (if
the input clock is output of global buffer), or global buffer option for source type. If the
input clock is used only by core, provide clock-capable pin as source type.
Clocking
Up to seven output clocks with different frequencies can be generated for required circuitry.
Resets
•
Clocking Wizard has active high Asynchronous reset signal for clocking primitive.
•
The core must be held in reset during clock switch over.
•
When the input clock or feedback clock is lost, the clkinstopped or clkfbstopped
status signal is asserted. After the clock returns, the clkinstopped signal is
unasserted and a reset must be applied.
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Chapter 3: Designing with the Core
Functional Overview
The Clocking Wizard is an interactive Graphical User Interface (GUI) that creates a clocking
network based on design-specific needs. The required clock network parameters are
organized in a linear sequence so that you can select only the desired parameters. Using the
wizard, experienced users can explicitly configure their chosen clocking primitive, while less
experienced users can let the wizard automatically determine the optimal primitive and
configuration - based on the features required for their individual clocking networks.
If you are already familiar with the Digital Clock Manager (DCM) and Phase-Locked Loop
(PLL) wizards, refer to Appendix B, Migrating for information on usage differences.
Clocking Features
Major clocking-related functional features desired and specified can be used by the wizard
to select an appropriate primitive. Incompatible features are automatically dimmed out to
help the designer evaluate feature trade-offs.
Clocking features include
•
Frequency synthesis
•
Phase alignment
•
Spread Spectrum
•
Minimization of output jitter
•
Allowance of larger input jitter
•
Minimization of power
•
Dynamic phase shift
•
Dynamic reconfiguration
•
Safe Clock Startup and Sequencing
Input Clocks
One input clock is the default behavior, but two input clocks can be chosen by selecting a
secondary clock source. Only the timing parameters of the input clocks in their specified
units is required; the wizard uses these parameters as needed to configure the output
clocks.
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Chapter 3: Designing with the Core
Input Clock Jitter Option
The wizard allows you to specify the input clock jitter either in UI or PS units using a
drop-down menu.
Output Clocks
The number of output clocks is user-configurable. The maximum number allowed depends
upon the selected device or primitive and the interaction of the major clocking features you
specify. For MMCM(E2/E3) maximum seven, PLLE2 maximum six and PLLE3 maximum two
output clocks can be configured. Input the desired timing parameters (frequency, phase,
and duty cycle) and let the clocking wizard select and configure the clocking primitive and
network automatically to comply with the requested characteristics. If it is not possible to
comply exactly with the requested parameter settings due to the number of available input
clocks, best-attempt settings are provided. When this is the case, the clocks are ordered so
that clk_out1 is the highest-priority clock and is most likely to comply with the requested
timing parameters. The wizard prompts you for frequency parameter settings before the
phase and duty cycle settings.
TIP: The port names in the generated circuit can differ from the port names used on the original
primitive.
Clock Buffering and Feedback
In addition to configuring the clocking primitive within the device, the wizard also assists
with constructing the clocking network. Buffering options are provided for both input and
output clocks. Feedback for the primitive can be user-controlled or left to the wizard to
automatically connect. If automatic feedback is selected, the feedback path is matched to
timing for clk_out1.
Optional Ports
All primitive ports are available for user-configuration. You can expose any of the ports on
the clocking primitive, and these are provided as well in the source code.
Primitive Override
All configuration parameters are also user-configurable. In addition, should a provided
value be undesirable, any of the calculated parameters can be overridden with the desired
settings.
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Chapter 3: Designing with the Core
Summary
The Clocking Wizard provides a summary for the created network. Input and output clock
settings are provided both visually and as constraint files. In addition, jitter numbers for the
created network are provided along with a resource estimate. Lastly, the wizard provides the
input setting for PLL and MMCM based designs for Xilinx Power Estimator (XPE) in an
easy-to-use table.
Design Environment
Figure 3-1 shows the design environment provided by the wizard to assist in integrating the
generated clocking network into a design. The wizard provides a synthesizable and
downloadable example design to demonstrate how to use the network and allows you to
place a very simple clocking network in your device. A sample simulation test bench, which
simulates the example design and illustrates output clock waveforms with respect to input
clock waveforms, is also provided.
X-Ref Target - Figure 3-1
$EMONSTRATION4EST"ENCH
%XAMPLE$ESIGN
0ROVIDED#LOCKING.ETWORK
/PTIONAL
#LOCK
'ENERATORS
)NPUT
#LOCKS
"UFS
&REQUENCY
#HECK
/PTIONAL&EEDBACK
/PTIONAL
#ONFIGURED
#LOCKING
0RIMITIVE
"UFS
/UTPUT
#LOCKS
#OUNTER
!RRAY
(IGH
"ITS
8
Figure 3-1:
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Chapter 3: Designing with the Core
Core Architecture
The Clocking Wizard generates source code HDL to implement a clocking network. The
generated clocking network typically consists of a clocking primitive (MMCM(E2/E3)_ADV
or PLL(E2/E3)_ADV) plus some additional circuitry which typically includes buffers and
clock pins. The network is divided into segments as illustrated in Figure 3-2. Details of these
segments are described in the following sections.
X-Ref Target - Figure 3-2
0ROVIDED#LOCKING.ETWORK
/PTIONALFEEDBACK
)NPUT
#LOCKS
#ONFIGURED
#LOCKING
0RIMITIVE
/PT
"UFS
/PT
"UFS
/UTPUT
#LOCKS
8
Figure 3-2:
Provided Clocking Network
Input Clocks
Up to two input clocks are available for the clocking network. Buffers are optionally inserted
on the input clock paths based on the buffer type that is selected.
Primitive Instantiation
The primitive, either user or wizard selected, is instantiated into the network. Parameters on
primitives are set by the wizard, and can be overridden by you. Unused input ports are tied
to the appropriate values. Unused output ports are labeled as such.
Feedback
If phase alignment is not selected, the feedback output port on the primitive is
automatically tied to the feedback input port. If phase alignment with automatic feedback
is selected, the connection is made, but the path delay is matched to that of clk_out1. If
user-controlled feedback is selected, the feedback ports are exposed.
Output Clocks
Buffers that are user-selected are added to the output clock path, and these clocks are
provided.
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Chapter 3: Designing with the Core
I/O Signals
All ports are optional, with the exception that at least one input and one output clock are
required. Availability of ports is controlled by user-selected parameters. For example, when
Dynamic Reconfiguration is selected, only those ports related to Dynamic Reconfiguration
are exposed. Any port that is not exposed is either tied off or connected to a signal labeled
unused in the delivered source code.
IMPORTANT: Not all ports are available for all devices or primitives; for example, Dynamic Phase Shift
is not available when Spread Spectrum is selected.
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Chapter 4
Design Flow Steps
This chapter describes customizing and generating the core, constraining the core, and the
simulation, synthesis and implementation steps that are specific to this IP core. More
detailed information about the standard Vivado® design flows in the IP Integrator can be
found in the following Vivado Design Suite user guides:
•
Vivado Design Suite User Guide: Designing IP Subsystems using IP Integrator (UG994)
[Ref 7]
•
Vivado Design Suite User Guide: Designing with IP (UG896) [Ref 2]
•
Vivado Design Suite User Guide: Getting Started (UG910) [Ref 4]
•
Vivado Design Suite User Guide: Logic Simulation (UG900) [Ref 5]
Customizing and Generating the Core
Vivado Integrated Design Environment (IDE)
You can customize the IP for use in your design by specifying values for the various
parameters associated with the IP core using the following steps:
1. Select the IP from the IP catalog.
2. Double-click on the selected IP or select the Customize IP command from the toolbar or
popup menu.
For details, see the sections, “Working with IP” and “Customizing IP for the Design” in the
Vivado Design Suite User Guide: Designing with IP (UG896) [Ref 2] and the “Working with the
Vivado IDE” section in the Vivado Design Suite User Guide: Getting Started (UG810) [Ref 4].
If you are customizing and generating the core in the Vivado IP Integrator, see the Vivado
Design Suite User Guide: Designing IP Subsystems Using IP Integrator (UG994) [Ref 7] for
detailed information. IP Integrator might auto-compute certain configuration values when
validating or generating the design. To check whether the values do change, see the
description of the parameter in this chapter. To view the parameter value you can run the
validate_bd_design command in the Tcl console.
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Chapter 4: Design Flow Steps
Note: Figures in this chapter are illustrations of the Vivado IDE. This layout might vary from the
current version.
Clock Manager Type (Primitive Selection)
In Zynq®-7000 and 7 series devices, MMCME2 and PLLE2 primitives are available for the
clocking needs. In UltraScale architecture, MMCME3 and PLLE3 primitives are available for
clocking needs. You have the option to configure either of these by selecting the primitive.
Features are enabled or disabled depending on the primitive selected.
Clocking Features
The first page of the GUI (Figure 4-1, Figure 4-2) allows you to identify the required
features of the clocking network and configure the input clocks.
X-Ref Target - Figure 4-1
Figure 4-1:
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Chapter 4: Design Flow Steps
<><><><><>
X-Ref Target - Figure 4-2
X-Ref Target - Figure 4-3
Figure 4-2:
Clocking Options for 7 Series MMCM (Spread Spectrum Selected)
Selecting Clocking Features
The available clocking features are shown for the selected target device. You can select as
many features as desired; however, some features consume additional resources, and some
can result in increased power consumption. Additionally, certain combinations of features
are not allowed.
When using IP Integrator, Frequency, Phase and Clock Domain properties of the output
clocks are automatically propagated and any change on input clock properties reflect on all
the outputs.
Clocking features include:
•
Frequency synthesis. This feature allows output clocks to have different frequencies
than the active input clock.
•
Spread Spectrum (SS). This feature provides modulated output clocks which reduces
the spectral density of the electromagnetic interference (EMI) generated by electronic
devices. This feature is available only for MMCM(E2/E3) primitive. Minimize power,
Dynamic Reconfig features are not available when Spread Spectrum is TRUE.
•
Phase alignment. This feature allows the output clock to be phase locked to a
reference, such as the input clock pin for a device.
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Chapter 4: Design Flow Steps
•
Minimize power. This features minimizes the amount of power needed for the
primitive at the possible expense of frequency, phase offset, or duty cycle accuracy. This
feature is not available when Spread Spectrum feature is selected.
•
Dynamic phase shift. This feature allows you to change the phase relationship on the
output clocks. This feature is not available when Spread Spectrum feature is selected.
•
Dynamic reconfiguration. This feature allows you to change the programming of the
primitive after device configuration. When this option is chosen, AXI4-Lite interface is
selected by default for reconfiguring clocking primitive. DRP interface can be selected
if direct access to MMCM/PLL DRP register is required. Refer to Dynamic
Reconfiguration through AXI4-Lite for more information.
•
Balanced. Selecting Balanced results in the software choosing the correct BANDWIDTH
for jitter optimization.
•
Minimize output jitter. This feature minimizes the jitter on the output clocks, but at
the expense of power and possibly output clock phase error. This feature is not
available with 'Maximize input jitter filtering'.
•
Maximize input jitter filtering. This feature allows for larger input jitter on the input
clocks, but can negatively impact the jitter on the output clocks. This feature is not
available with 'Minimize output jitter'.
•
Safe Clock Startup and Sequencing. Safe Clock Startup feature enables stable and
valid clock at the output using BUFGCE after Locked is sampled High for 8 input clocks.
Sequencing feature enables Clocks in a sequence according to the number entered
through GUI. Delay between two enabled output clocks in sequence is 8 cycle of
second clock in the sequence clock. This feature is useful for a system where modules
need to be start operating one after the other.
Configuring Input Clocks
There are two input clocks available and depending on selection reference clock can be
switched from one to another. GUI provides option to select the secondary input clock to
enable the additional input clock. If Spread Spectrum feature is selected, secondary input
clock is disabled in the Clocking wizard. Depending on the frequency of the secondary input
clock, this can cause a less ideal network to be created than might be possible if just the
primary input clock was present (more output jitter, higher power, etc.)
Valid input frequency ranges are:
Frequency when SS is unselected: 10 – 1066 MHz
Frequency when SS is selected:
25 – 150 MHz
Enter the frequency and peak-to-peak period (cycle) jitter for the input clocks. The wizard
then uses this information to create the clocking network. Additionally, a XDC (Xilinx Design
Constraints file) is created using the values entered. For the best calculated clocking
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Chapter 4: Design Flow Steps
parameters, it is best to fully specify the values. For example, for a clock requirement of 33
1/3 MHz, enter 33.333 MHz rather than 33 MHz.
You can select which buffer type drives your input clock, and this is then instantiated in the
provided source code. If your input buffers are located externally, selecting "No buffer"
leaves the connection blank. If Phase Alignment is selected, you do not have access to pins
that are not dedicated clock pins, because the skew introduced by a non-clock pin is not
matched by the primitive. You can choose the units for input clock jitter by selecting either
the UI or PS drop-down menu. The input jitter box accepts the values based on this
selection.
Output Clock Settings
The second page of the GUI (Figure 4-3) configures requirements for the output clocks.
Each selected output clock can be configured on this screen.
X-Ref Target - Figure 4-3
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Chapter 4: Design Flow Steps
Configuring Output Clocks
To enable an output clock, click on the box located next to it. Output clocks must be
enabled sequentially.
You can specify values for the output clock frequency, phase shift, and duty cycle assuming
that the primary input clock is the active input clock. The Clocking Wizard attempts to
derive a clocking network that meets your criteria exactly. In the event that a solution
cannot be found, best attempt values are provided and are shown in the actual value
column. Achieving the specified output frequency takes precedence over implementing the
specified phase, and phase in turn takes higher precedence in the clock network derivation
process than duty cycle. The precedence of deriving the circuits for the clk_out signals is
clk_out1 > clk_out2 > clk_out3, and so on. Therefore, finding a solution for
clk_out1 frequency has a higher priority. Values are recalculated every time an input
changes. Because of this, it is best to enter the requirements from top to bottom and left to
right. This helps to pinpoint requested values that cannot be supported exactly. If phase
alignment is selected, the phase shift is with respect to the active input clock.
If 180° phase shift is requested on Clk_out2, clk_out3, clk_out4, or clk_out5, then
the Wizard connects any of these clocks to previous clocks Inverted clock outputs
(clkout[0:3]B) of MMCM/PLL, as compared to the previous clock and other properties
like Frequency, duty cycle, etc., are identical to the previous clock. Consider that clk_out1
is configured with 100 MHz and 0° phase shift and clk_out2 is configured 100 MHz with
180° phase shift. Then clk_out2 is connected to clkout0b. If clk_out1 and clk_out2
are 180° phase shifted and CLK_OUT2 and clk_out3 are 180° phase shifted, then
clk_out3 uses it’s own phase settings and is connected to clkout2 of MMCM. If you have
another clock CLK_OUT4 with 180° phase shift compared to clk_out3, then clk_out4 is
connected to clkout2b.
You can choose which type of buffer is instantiated to drive the output clocks, or "No
buffer" if the buffer is already available in external code. The buffers available depend on
your device family. For all outputs that have BUFR as the output driver, the "BUFR_DIVIDE"
attribute is available as a generic parameter in the HDL. You can change the divide value of
the BUFR while instantiating the design.
If you choose the Dynamic phase shift clocking, the 'Use Fine Ps' check boxes are available.
'Use Fine Ps' allows you to enable the Variable Fine Phase Shift on MMCM(E2/E3). Select the
appropriate check box for any clock that requires dynamic phase shift. The wizard resets the
requested phase field to "0.000" when 'Use Fine Ps' is selected.
When Safe Clock Startup feature is enabled on the first tab of the GUI, the Use Clock
Sequencing table is active and Sequence number for each enabled clock is available for the
configuration. In this mode only BUFGCE is allowed as Drives of the clock outputs.
Both 7 series and UltraScale devices support MMCM fractional divide functionality in
increments of 1/8th (0.125) for CLKFBOUT and CLKOUT0, and can support greater clock
frequency synthesis.
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Chapter 4: Design Flow Steps
The resolution of the fractional divide is 1/8 or 0.125 degrees, effectively increasing the
number of synthesizeable frequencies by a factor of eight. For example, if the CLKIN
frequency is 100 MHz and the M divide value is set to 8, then the VCO frequency is 800 MHz.
CLKOUT0 can be used to further fractionally divide the 800 MHz VCO frequency (for
example, CLKOUT0_DIVIDE = 2.5 resulting in a 320 MHz output frequency).
When using the fractional divider, the duty cycle is not programmable for outputs used in
the fractional mode.
Fractional divide is not allowed in either fixed or dynamic phase-shift mode. CDDC feature
is not available in the fractional divide mode for UltraScale devices.
Refer to 7 Series FPGAs Clocking Resources User Guide (UG47) [Ref 9] and UltraScale
Architecture Clocking Resources User Guide (UG572) [Ref 8] for more information.
X-Ref Target - Figure 4-4
Figure 4-4:
Output Clocks with Safe Clock Start Up and Clock Sequencing for 7 Series MMCM
You can configure the sequence number from 1 to the maximum number of clocks selected.
Clocking Wizard does not allow any break in the sequence from one to maximum in the
table. Clock Frequency of the output clock in Sequence should not be more than eight times
of the output clock next in sequence.
For details of the clocking behavior in this mode, refer to Figure 4-5 and Figure 4-6.
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Chapter 4: Design Flow Steps
X-Ref Target - Figure 4-5
%8)*&(
%8)*&(
$&/.
'
/2&.
'
%8)+
4
%LW6KLIW5HJ
4
%8)+
%LW6KLIW5HJ
&/.287
%&/.
,1,7 ,1,7 &/.287
00&0
;
Figure 4-5:
Safe Clock Start Up
X-Ref Target - Figure 4-6
%8)*&(
%8)*&(
$&/.
'
/2&.
'
4
%LW6KLIW5HJ
&/.287
%8)+
%&/.
4
%LW6KLIW5HJ
%8)+
,1,7 ,1,7 &/.287
00&0
;
Figure 4-6:
Safe Clock Start Up with Sequencing
When Spread Spectrum (SS) is selected, CLK_OUT<3> and CLK_OUT<4> are not available.
Divide values of these outputs are used for SS modulation frequency generation.
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Chapter 4: Design Flow Steps
X-Ref Target - Figure 4-7
Figure 4-7:
Output Clocks for 7 Series MMCM (Spread Spectrum Selected)
There are four modes available for SS Mode:
•
DOWN_LOW
•
DOWN_HIGH
•
CENTER_LOW
•
CENTER_HIGH
Available Modulation Frequency range is 25 – 250 KHz
Spread Spectrum calculation details are described in Figure 4-8 and Figure 4-9.
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Chapter 4: Design Flow Steps
X-Ref Target - Figure 4-8
&REQUENCY
#ENTER3PREAD
!VERAGE
&REQUENCY
3PREAD
-ODULATION&REQUENCY++
4IME
8
Figure 4-8:
Spread Spectrum Mode (Center Spread)
X-Ref Target - Figure 4-9
&REQUENCY
$OWN3PREAD
!VERAGE
&REQUENCY
3PREAD
-ODULATION&REQUENCY++
4IME
8
Figure 4-9:
Spread Spectrum Mode (Down Spread)
Note: Input_clock_frequency is in Hz unit.
For spread:
•
If (SS_Mode = CENTER_HIGH) :=>
°
•
If (SS_Mode = CENTER_LOW) :=>
°
•
spread (ps) = +/- [1/(Input_clock_frequncy*(M-0.125*4)/D/O) - 1/
(Input_clock_frequency*M/D/O)]
If (SS_Mode = DOWN_HIGH) :=>
°
•
spread (ps) = +/- [1/(Input_clock_frequncy*(M-0.125*4)/D/O) - 1/
(Input_clock_frequency*M/D/O)]
spread (ps) = + [1/(Input_clock_frequncy*(M-0.125*4)/D/O) - 1/
(Input_clock_frequency*M/D/O)]
If (SS_Mode = DOWN_LOW) :=>
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Chapter 4: Design Flow Steps
°
spread (ps) = + [1/(Input_clock_frequncy*(M-0.125*4)/D/O) - 1/
(Input_clock_frequency*M/D/O)]
Where M is CLKFBOUT_MULT_F, D is DIVCLK_DIVIDE, and O is respective CLKOUTx_DIVIDE.
•
For Modulation Frequency:
°
O2 and O3 are calculated by the bitgen in implementation. Same calculation is done
in the wizard to get actual modulation frequency value.
°
Then based on what O2 and O3 is calculated, the actual modulation frequency is
calculated:
•
If (SS_Mode = CENTER_HIGH or SS_Mode = CENTER_LOW)
Actual_modulation_frequency (average) = (Input_clock_frequency*M/D) / (O2 * O3) / 16
•
If (SS_Mode = DOWN_HIGH) Actual_modulation_frequency (average) = 0.5 *
[((Input_clock_frequency*M/D) / (O2 * O3) / 8) + ((Input_clock_frequency*(M-0.5)/D) /
(O2 * O3) / 8)]
•
If (SS_Mode = DOWN_LOW) Actual_modulation_frequency (average) = 0.5 *
[((Input_clock_frequency*M/D) / (O2 * O3) / 8) + ((Input_clock_frequency*(M-0.25)/D) /
(O2 * O3) / 8)]
IMPORTANT: Actual modulation frequency may deviate within +/- 10% of the requested modulation
frequency for some settings.
Selecting Optional Ports
All other optional ports that are not handled by selection of specific clocking features are
listed under Optional Inputs/Outputs. Click to select the ports that you wish to make visible;
inputs that are unused are tied off appropriately, and outputs that are unused are labeled as
such in the provided source code.
Reset Type
You can select Reset Type as Active High or Active Low when RESET is enabled. Default
value is Active High.
RECOMMENDED: Xilinx recommends using the Active High reset in the design.
Choosing Feedback
Feedback selection is only available when phase alignment is selected. When phase
alignment is not selected, the output feedback is directly connected to the input feedback.
For designs with phase alignment, choose automatic control on-chip if you want the
feedback path to match the insertion delay for CLK_OUT1. You can also select
user-controlled feedback if the feedback is in external code. If the path is completely on the
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Chapter 4: Design Flow Steps
FPGA, select on-chip; otherwise, select off-chip. For designs that require external feedback
and related I/O logic, choose automatic control off-chip feedback. You can choose either
single-ended or differential feedback in this mode. The wizard generates the core logic and
logic required to route the feedback signals to the I/O.
The third GUI screen (Figure 4-7) provides information to configure the rest of the clocking
network.
Output Clock Jitter and Phase Error
You can query the jitter and phase error on any of the output clocks of Clocking Wizard IP
core. For example, if core name is clk_wiz_0, then by using following commands, jitter and
phase error for clk_out1 are available in Tcl console.
get_property CONFIG.CLKOUT1_JITTER [get_ips clk_wiz_0]
get_property CONFIG.CLKOUT1_PHASE_ERROR [get_ips clk_wiz_0]
Primitive Overrides
One or more pages of device and primitive specific parameter overrides are displayed.
Overriding Calculated Parameters
The Clocking Wizard selects optimal settings for the parameters of the clocking primitive.
You can override any of these calculated parameters if you wish. By selecting Allow
override mode, the overridden values are used rather than the calculated values as
primitive parameters. The wizard uses the settings as shown on this screen for any timing
calculations, and any settings changed here are reflected in the summary pages.
IMPORTANT: It is important to verify that the values you are choosing to override are correct because
the wizard implements what you have chosen even if it causes issues with the generated network.
Parameters listed are relevant for the physical clocks on the primitive, rather than the
logical clocks created in the source code. For example, to modify the settings calculated for
the highest priority CLK_OUT1, you actually need to modify CLKOUT0* parameters, and not
the CLKOUT1* parameters for a MMCME2 or PLLE2.
The generated source code contains the input and output clock summaries shown in the
next summary page, as shown in Figure 4-10.
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Chapter 4: Design Flow Steps
X-Ref Target - Figure 4-10
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Chapter 4: Design Flow Steps
X-Ref Target - Figure 4-11
Figure 4-11:
Primitive Override Screen (Spread Spectrum Selected)
Port Renaming
The first summary page (Figure 4-13) displays summary information about the input and
output clocks. This information is also provided as comments in the generated source code,
and in the provided XDC.
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Chapter 4: Design Flow Steps
X-Ref Target - Figure 4-12
Figure 4-12:
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Chapter 4: Design Flow Steps
X-Ref Target - Figure 4-13
Figure 4-13:
Port Renaming (Spread Spectrum Selected)
Input Clocking Summary
Information entered on the first page of the GUI is shown for the input clocks.
Output Clocking Summary
Derived timing information for the output clocks is shown. If the chosen primitive has an
oscillator, the VCO frequency is provided as reference. If you have a secondary input clock
enabled, you can choose which clock is used to calculate the derived values. When Spread
Spectrum is enabled, actual modulation frequency is provided as reference.
Tspread is the actual spread as calculated in Configuring Output Clocks.
Port Names
The Wizard allows you to name the ports according to their needs. If you want to name the
HDL port for primary clock input, simply type in the port name in the adjacent text box. The
text boxes contain the default names. In the case of Primary clock input, the default name
is CLK_IN1.
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Chapter 4: Design Flow Steps
IMPORTANT: Be careful when changing the port names, as it could result in syntax errors if the port
name entered is any reserved word of VHDL or Verilog or if that signal is already declared in the
module.
Summary
The summary page (Figure 4-14) contains general summary information.
X-Ref Target - Figure 4-14
Figure 4-14:
Summary Screen
Resource Estimate Summary
A resource estimate is provided based on the chosen clocking features.
XPower Estimator Summary
Input parameters to the Xpower tool are provided.
Dynamic Reconfiguration through AXI4-Lite
The Clocking Wizard core provides an AXI4-Lite interface for the dynamic reconfiguration
of the clocking primitive MMCM/PLL. This interface is enabled when Dynamic Reconfig is
enabled and Interface selection is AXI4-Lite. This feature is not supported when Spread
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Chapter 4: Design Flow Steps
Spectrum is enabled. Mixed language RTL is delivered by the core when AXI4-Lite interface
is used. For reconfiguring Phase and Duty Cycle, set Phase Duty Cycle config to True. This
configuration utilizes DSP resources. By default, this option is set to False to optimize the
design for area. Resource utilization for the AXI4-Lite interface configuration of Clocking
Wizard IP core using Kintex-7 part xc7k325t is described in Table 4-1.
Table 4-1:
Kintex-7 FPGA Resource Utilization with AXI4-Lite Interface
Site Type
Used when Phase Duty Cycle
config = false
Used when Phase Duty Cycle
config = true
Slice LUTs
1071
15323
Slice Registers
1426
1504
DSPs
0
38
Table 2-2 provides details of the signals of AXI4-Lite and Table 4-2 provides details of the
clock configuration registers.
The Clocking Wizard core uses a configuration state machine listed in MMCM and PLL
Dynamic Reconfiguration [Ref 6] and extends from two fixed state configuration to program
any valid range of Multiply, Divide, Phase and Duty Cycle. In this state machine, State 1
corresponds to default state configured through Clocking Wizard interface. State 2
corresponds to user-configuration loaded into the clock configuration register detailed in
Table 4-2. State 2 values are also initialized with the State 1 values so that a valid
configuration is stored by default. You should update only those registers which are
required to change the output clock behavior.
You should first write all the required clock configuration registers and then check for the
status register. If status register value is 0x1, start the reconfiguration by writing Clock
Configuration Register 23 with 0x7. The next write should be 0x2 before the Locked goes
High. If the original configuration is needed at any time, then writing this register with value
0x4 and then 0x0 restores the original settings.
Before writing into C_BASEADDR + 0x200 register detailed in table 4-2, please make sure
that these values result in a valid VCO frequency range of MMCM/PLL which is calculated
using the equation:
VCO Frequency = (Input Clock Frequency) * (CLKFBOUT_MULT)/DIVCLK_DIVIDE
For details on the VCO range, refer to the DC and Switching Characteristics section of the
applicable device data sheet.
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Chapter 4: Design Flow Steps
X-Ref Target - Figure 4-15
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567
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Figure 4-15:
Table 4-2:
Dynamic Reconfiguration using AXI4-Lite Interface
Clock Configuration Registers
Base Address + Offset
(hex)
Register
Name
Reset
Value
(hex)
Access
Type
C_BASEADDR + 0x00
Software Reset
Register (SRR)
N/A
W(1)
C_BASEADDR + 0x04
Status Register
(SR)
0x00000000
R
C_BASEADDR + 0x200
Clock
Configuration
Register 0
Default(2) :
0x01010A00
R/W
Description
Software Reset Register
To activate software reset, the value
0x0000_000A must be written to the
register. Any other access, read or write,
has undefined results.
Status Register
Bit[0] = Locked
When ‘1’ MMCM/PLL is Locked and ready
for the reconfiguration. Status of this bit is
‘0’ during the reconfiguration.
Bit[7:0] = DIVCLK_DIVIDE
Eight bit divide value applied to all output
clocks.
Bit[15:8] = CLKFBOUT_MULT
Integer part of multiplier value i.e. For 8.125,
this value is 8 = 0x8.
Bit[25:16] = CLKFBOUT_FRAC Multiply(3)
Fractional part of multiplier value i.e. For
8.125, this value is 125 = 0x7D.
Bit[26] = CLKFBOUT_FRAC_EN (3)
This bit should be set to 1 for Fractional
multiplication.
Setting this bit to 0 uses the default
configuration.
The value of CLKFBOUT fractional divide
can be from 0 to 875 representing the
factional multiplied by 1000.
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Table 4-2:
Clock Configuration Registers (Cont’d)
Base Address + Offset
(hex)
Register
Name
Reset
Value
(hex)
Access
Type
Description
C_BASEADDR + 0x204
Clock
Configuration
Register 1
Default(2) :
0x00000000
R/W
Bit[31:0] = CLKFBOUT_PHASE
Phase values entered are Signed Number
for +/- phase.
C_BASEADDR + 0x208
Clock
Configuration
Register 2
Default(2) :
0x0004000a
R/W
Bit[7:0] = CLKOUT0_DIVIDE
Integer part of clkout0 divide value
For example, for 2.250, this value is 2 = 0x2
Bit[17:8] = CLKOUT0_FRAC Divide(3)
Fractional part of clkout0 divide value
For example, for 2.250, this value is 250 =
0xFA
Bit[18] = CLKOUT0_FRAC_EN (3)
This bit should be set to 1 for Fractional
division
C_BASEADDR + 0x20C
Clock
Configuration
Register 3
Default(2) :
0x00000000
R/W
Bit[31:0] = CLKOUT0_PHASE(5)
C_BASEADDR + 0x210
Clock
Configuration
Register 4
Default(2) :
0x0000C350
R/W
Bit[31:0] = CLKOUT0_DUTY
Duty cycle value = (Duty Cycle in %) * 1000
For example, for 50% duty cycle, value is
50000 = 0xC350
C_BASEADDR + 0x214
Clock
Configuration
Register 5
Default(2) :
0x0000000A
R/W
Bit[7:0] = CLKOUT1_DIVIDE(4)
Eight bit clkout1 divide value
C_BASEADDR + 0x218
Clock
Configuration
Register 6
Default(2) :
0x00000000
R/W
Bit[31:0] = CLKOUT1_PHASE(5)
Phase values entered are Signed Number
for +/- phase
C_BASEADDR + 0x21C
Clock
Configuration
Register 7
Default(2) :
0x0000C350
R/W
Bit[31:0] = CLKOUT1_DUTY(6)
C_BASEADDR + 0x220
Clock
Configuration
Register 8
Default(2) :
0x0000000A
R/W
Bit[7:0] = CLKOUT2_DIVIDE(4)
C_BASEADDR + 0x224
Clock
Configuration
Register 9
Default(2) :
0x00000000
R/W
Bit[31:0] = CLKOUT2_PHASE(5)
C_BASEADDR + 0x228
Clock
Configuration
Register 10
Default(2) :
0x0000C350
R/W
Bit[31:0] = CLKOUT2_DUTY(6)
C_BASEADDR + 0x22C
Clock
Configuration
Register 11
Default(2) :
0x0000000A
R/W
Bit[7:0] = CLKOUT3_DIVIDE(4)
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Table 4-2:
Clock Configuration Registers (Cont’d)
Base Address + Offset
(hex)
Register
Name
Reset
Value
(hex)
Access
Type
Description
C_BASEADDR + 0x230
Clock
Configuration
Register 12
Default(2) :
0x00000000
R/W
Bit[31:0] = CLKOUT3_PHASE(5)
C_BASEADDR + 0x234
Clock
Configuration
Register 13
Default(2) :
0x0000C350
R/W
Bit[31:0] = CLKOUT3_DUTY(6)
C_BASEADDR + 0x238
Clock
Configuration
Register 14
Default(2) :
0x0000000A
R/W
Bit[7:0] = CLKOUT4_DIVIDE(4)
C_BASEADDR + 0x23C
Clock
Configuration
Register 15
Default(2) :
0x00000000
R/W
Bit[31:0] = CLKOUT4_PHASE(5)
C_BASEADDR + 0x240
Clock
Configuration
Register 16
Default(2) :
0x0000C350
R/W
Bit[31:0] = CLKOUT4_DUTY(6)
C_BASEADDR + 0x244
Clock
Configuration
Register 17
Default(2) :
0x0000000A
R/W
Bit[7:0] = CLKOUT5_DIVIDE(4)
C_BASEADDR + 0x248
Clock
Configuration
Register 18
Default(2) :
0x00000000
R/W
Bit[31:0] = CLKOUT5_PHASE(5)
C_BASEADDR + 0x24C
Clock
Configuration
Register 19
Default(2) :
0x0000C350
R/W
Bit[31:0] = CLKOUT5_DUTY(6)
C_BASEADDR + 0x250 (3)
Clock
Configuration
Register 20
Default(2) :
0x0000000A
R/W
Bit[7:0] = CLKOUT6_DIVIDE(4)
C_BASEADDR + 0x254 (3)
Clock
Configuration
Register 21
Default(2) :
0x00000000
R/W
Bit[31:0] = CLKOUT6_PHASE(5)
C_BASEADDR + 0x258 (3)
Clock
Configuration
Register 22
Default(2) :
0x0000C350
R/W
Bit[31:0] = CLKOUT6_DUTY(6)
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Chapter 4: Design Flow Steps
Table 4-2:
Clock Configuration Registers (Cont’d)
Base Address + Offset
(hex)
C_BASEADDR + 0x25C
C_BASEADDR + 0x260 to
C_BASEADDR + 0x7FC
Reset
Value
(hex)
Access
Type
Clock
Configuration
Register 23
0x00000000
R/W
Undefined
Undefined
Register
Name
Description
Bit[0] = LOAD
Loads Clock Configuration Register values to
the internal register used for dynamic
reconfiguration. This bit should be
asserted when the required settings are
already written into Clock Configuration
Registers and then de-asserted with next
write.
Bit[1] = SADDR
When written 0, default configuration
done in the Clocking Wizard GUI is loaded
for dynamic reconfiguration.
When written 1, setting provided in the
Clock Configuration Registers are used for
dynamic reconfiguration.
Bit[2] = SEN
Writing 1 to this bit starts the dynamic
reconfiguration state machine. This bit
should be asserted and then deasserted
with next write.
Configuring this bit to 0 has no impact on
the configuration register values.
N/A (1)
Don’t read/write these registers.
1. Reading of this register returns an undefined value.
2. Initialized with configuration settings done by the clocking algorithm.
3. Valid only for MMCM(E2/E3) primitive
4. Eight bit divide value
5. Phase value = (Phase Requested) * 1000 i.e. for 45.5 degree phase, required value is 45500 = 0xB1BC.
6. Note: Phase values entered are Signed Number in the range +360000 to -360000
7. duty cycle value = (Duty Cycle in %) * 1000 i.e. for 50% duty cycle, value is 50000 = 0xC350
Examples Dynamic Reconfiguration through AXI4-Lite
The input and output clock frequencies are 100 MHz in the Clocking Wizard by default.
To achieve 200 MHz frequency on clkout1 in the Clocking Wizard core with primary input
clock frequency at 100 MHz (VCO frequency at 1000 MHz), perform the following steps:
1. Configure the Clock Configuration register 0 (Address: C_BASEADDR + 0x200) with
0x00000A01.
Writing this value sets DIVCLK_DIVIDE value to 1 and CLKFBOUT_MULT to 10.
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Chapter 4: Design Flow Steps
2. Configure the Clock Configuration Register 2 (Address: C_BASEADDR + 0x208) with
0x00000005.
Writing this value sets CLKOUT0_DIVIDE to 5. The VCO frequency being 1000 MHz,
dividing it by CLKOUT0_DIVIDE will give the 200 MHz frequency on the clkout1 in
the IP. Check for the status register, if the status register value is 0x1, then go to step 3.
3. Configure the Clock Configuration Register 23 (Address: C_BASEADDR + 0x25C) with
0x00000007 to set the LOAD and SEN bits.
4. Configure the Clock Configuration Register 23 (Address: C_BASEADDR + 0x25C) with
0x2 before the Locked goes High. This resets the LOAD and SEN bits.
5. Wait for the locked signal. The new frequency can be checked at clkout1 output port.
Note: You can reset to the default settings by configuring the Clock Configuration Register 23
(Address: C_BASEADDR + 0x25C) with the value 0x00000004, followed by writing 0x00000000
(SADDR bit is set to 0).
Refer to the Chapter 5, Detailed Example Design for more details.
Output Generation
For details, see “Generating IP Output Products” in the Vivado Design Suite User Guide:
Designing with IP (UG896) [Ref 2].
Constraining the Core
Required Constraints
At least one clock constraint is required for period and jitter.
create_clock -period 10.0 [get_ports clk_in1]
set_input_jitter [get_clocks -of_objects [get_ports clk_in1]] 0.1
The core level XDC has early processing order so core level XDC constraints are applied first
and then are overridden by the user-provided constraints.
Device, Package, and Speed Grade Selections
Supports all packages, speed grades and devices.
Clock Frequencies
See Maximum Frequencies in Chapter 2
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Chapter 4: Design Flow Steps
Clock Management
The core can generate a maximum of seven output clocks with different frequencies.
Clock Placement
No clock placement constraint is provided.
Banking
Bank selection is not provided in xdc file.
I/O Standard and Placement
No I/O or placement constraints are provided.
Simulation
For comprehensive information about Vivado ® simulation components, as well as
information about using supported third party tools, see the Vivado Design Suite User
Guide: Logic Simulation (UG900) [Ref 5].
You can simulate the example design using the open_example_project flow in Vivado
design tools.
If you open an example project, then the simulation scripts are generated in the working
directory in:
example_project/<component_name>_example/<component_name>_example.sim/sim_1/
You can run fast simulation using unifast_ver or unifast libraries of MMCME2_ADV and
PLLE2_ADV. This improves simulation runtime by 100X.
Simulation Waveforms for the Safe Clock Startup Feature
Simulation when Safe Clock Startup is true is illustrated in Figure 4-16.
X-Ref Target - Figure 4-16
Figure 4-16:
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Chapter 4: Design Flow Steps
Figure 4-17 illustrates simulation when Safe Clock Startup is true and Use Clock Sequencing
is true with required sequence number in the table as indicted in Figure 4-4.
X-Ref Target - Figure 4-17
Figure 4-17:
Simulation when Safe Clock Startup is true and Use Clock Sequencing is true
Synthesis and Implementation
For details about synthesis and implementation, see “Synthesizing IP” and “Implementing
IP” in the Vivado Design Suite User Guide: Designing with IP (UG896) [Ref 2].
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Chapter 5
Detailed Example Design
In Vivado design tools, the open_example_project [get_ips <component_name>]
parameter in tcl console invokes a separate example design project where it creates
<component_name>_exdes as top module for synthesis and <component_name>_tb as
top module for simulation. You can run implementation or simulation of the example
design from example project.
Directory and File Contents
The open_example_project [get_ips <component_name>] parameter creates
example_project directory in the working area.
Example design contains the counters on all the output clocks and MSBs of these counters
are used as output to observe on LEDs on board.
Example Design
The following files describe the example design for the Clocking Wizard core.
•
VHDL
<project_name>/<project_name>.srcs/sources_1/ip/<component_name>/example_design/
<component_name>_exdes.vhd
•
Verilog
<project_name>/<project_name>.srcs/sources_1/ip/<component_name>/example_design/
<component_name>_exdes.v
The top-level example designs adds clock buffers where appropriate to all of the input and
output clocks. All generated clocks drive counters, and the high bits of each of the counters
are routed to a pin. This allows the entire design to be synthesized and implemented in a
target device to provide post place-and-route gate-level simulation.
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Chapter 6
Test Bench
This chapter contains information about the provided test bench in the Vivado® Design
Suite environment.
The following files describe the demonstration test bench.
•
VHDL
<project_name>/<project_name>.srcs/sources_1/ip/<component_name>/simulation/
<component_name>_tb.vhd
•
Verilog
<project_name>/<project_name>.srcs/sources_1/ip/<component_name>/simulation/
<component_name>_tb.v
The demonstration test bench is a simple VHDL or Verilog program to exercise the example
design and the core. It does Frequency calculation and check of all the output clocks. It
reports all the output clock frequency and if any of the output clocks is not generating the
required frequency then it reports ERROR.
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Appendix A
Verification, Compliance, and
Interoperability
Simulation
Verified with all the supported simulators.
Hardware Testing
Hardware testing is performed for all the features on Kintex-7 KC705 Evaluation Kit using
the provided example design.
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Appendix B
Migrating
This information is provided to assist those designers who are experienced with the DCM
and PLL Architecture Wizards. It highlights the differences between the old and new cores.
Migrating to the Vivado Design Suite
For information about migrating to the Vivado Design Suite, see the ISE to Vivado Design
Suite Migration Guide (UG911) [Ref 1].
Differences between the Clocking Wizard and the
Legacy DCM and PLL Wizards
There are several changes to the GUI and the wizard use model as described in the
following subsections.
Primitive Selection
The old wizard required you to choose the correct GUI (DCM or PLL) before configuring the
desired primitive.
The new wizard automatically selects the appropriate primitive and configures it based on
desired parameters. You can choose to override this choice in the event that multiple
primitives are available, as is the case for the Spartan®-6 device family.
Symbol Pin Activation
The old wizard had a symbol with clickable pins to enable a port.
For the new wizard, the symbol shows the ports that are currently active. To enable a port,
enable the appropriate feature in the GUI. For example, enabling the secondary input clock
enables the CLK_IN2 and CLK_IN_SEL ports and activates those ports in the symbol.
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Appendix B: Migrating
Parameter Override
The new wizard allows you to override any calculated parameter within the wizard by
switching to override mode.
Port Display Conventions
The new wizard displays the superset of ports covering all device families. Ports that are not
available for the selected target device are dimmed out. For example, if a Virtex®-6 device
is selected, the STATUS port is dimmed out because it is not available for devices in that
family. Information on the legal ports for a specific primitive can be found in the device
family-specific FPGA or clocking resources User Guide at www.xilinx.com/support/
documentation/index.htm.
Visibility of Clock Ports
The new wizard provides a clocking network that matches your requirements rather than
making clock ports visible. As a result, your clock names will not match the exact names for
the primitive. For example, while the “first” clock available for the Virtex-6 FPGA MMCM is
CLKOUT0, the highest priority clock available to you is actually named CLK_OUT1.
IMPORTANT: This change in numbering is especially important to consider if parameter overriding is
desired.
GUI Information Gathering Order
Some of the information-gathering ordering has changed. For the new wizard the general
flow is:
1. Select the clocking features.
2. Configure the input clock parameters.
3. Configure the output clock parameters.
4. Choose feedback and optional ports
5. View (and optionally override) calculated parameters.
6. Final summary pages.
For cascading clocking components, non-buffered input and output clocks are available for
easy connection.
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Appendix B: Migrating
Upgrading in the Vivado Design Suite
This section provides information about any changes to the user logic or port designations
that take place when you upgrade to a more current version of this IP core in the Vivado
Design Suite.
Parameter Changes
Added the INTERFACE_SELECTION parameter in the IDE for selecting the AXI4-Lite, DRP
or None for DRP register access.
CLKOUT<1-7>_JITTER parameter added to query the Peak to Peak Jitter on the output
clocks
CLKOUT<1-7>_PHASE_ERROR parameter added to query the phase error on the output clock.
Port Changes
Added optional AXI4-Lite ports (s_axi_*). See Table 2-4.
Other Changes
Improved safe clock logic to remove glitches on clock outputs for odd multiples of input
clock frequencies.
Xilinx does not recommend to upgrading the Clocking Wizard IP that has been targeted on
a board to a device part. For assistance, contact Xilinx Support.
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Appendix C
Debugging
This appendix includes details about resources available on the Xilinx Support website and
debugging tools.
Finding Help on Xilinx.com
To help in the design and debug process when using the Clocking Wizard core, the Xilinx
Support web page (www.xilinx.com/support) contains key resources such as product
documentation, release notes, answer records, information about known issues, and links
for opening a Technical Support WebCase.
Documentation
This product guide is the main document associated with the Clocking Wizard core. This
guide, along with documentation related to all products that aid in the design process, can
be found on the Xilinx Support web page (www.xilinx.com/support) or by using the Xilinx
Documentation Navigator.
Download the Xilinx Documentation Navigator from the Design Tools tab on the Downloads
page (www.xilinx.com/download). For more information about this tool and the features
available, open the online help after installation.
Solution Centers
See the Xilinx Solution Centers for support on devices, software tools, and intellectual
property at all stages of the design cycle. Topics include design assistance, advisories, and
troubleshooting tips.
Answer Records
Answer Records include information about commonly encountered problems, helpful
information on how to resolve these problems, and any known issues with a Xilinx product.
Answer Records are created and maintained daily ensuring that users have access to the
most accurate information available.
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Appendix C: Debugging
Answer Records for this core are listed below, and can also be located by using the Search
Support box on the main Xilinx support web page. To maximize your search results, use
proper keywords such as
•
Product name
•
Tool message(s)
•
Summary of the issue encountered
A filter search is available after results are returned to further target the results.
Answer Records for the Clocking Wizard core
AR 54102
http://www.xilinx.com/support/answers/54102.htm
Contacting Technical Support
Xilinx provides technical support at www.xilinx.com/support for this LogiCORE™ IP product
when used as described in the product documentation. Xilinx cannot guarantee timing,
functionality, or support of product if implemented in devices that are not defined in the
documentation, if customized beyond that allowed in the product documentation, or if
changes are made to any section of the design labeled DO NOT MODIFY.
Xilinx provides premier technical support for customers encountering issues that require
additional assistance.
To contact Xilinx Technical Support:
1. Navigate to www.xilinx.com/support.
2. Open a WebCase by selecting the WebCase link located under Support Quick Links.
When opening a WebCase, include:
•
Target FPGA including package and speed grade.
•
All applicable Xilinx Design Tools and simulator software versions.
•
Additional files based on the specific issue might also be required. See the relevant
sections in this debug guide for guidelines about which file(s) to include with the
WebCase.
Note: Access to WebCase is not available in all cases. Please login to the WebCase tool to see your
specific support options.
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Appendix C: Debugging
Debug Tools
There are many tools available to address Clocking Wizard core design issues. It is important
to know which tools are useful for debugging various situations.
Vivado Lab Edition
Vivado® Lab Edition inserts logic analyzer and virtual I/O cores directly into your design.
Vivado Lab Edition also allows you to set trigger conditions to capture application and
integrated block port signals in hardware. Captured signals can then be analyzed. This
feature in the Vivado IDE is used for logic debugging and validation of a design running in
Xilinx.
The Vivado logic analyzer is used to interact with the logic debug LogiCORE IP cores,
including:
•
ILA 2.0 (and later versions)
•
VIO 2.0 (and later versions)
See Vivado Design Suite User Guide: Programming and Debugging (UG908) [Ref 3].
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Appendix C: Debugging
Hardware Debug
Hardware issues can range from link bring-up to problems seen after hours of testing. This
section provides debug steps for common issues. The ChipScope debugging tool is a
valuable resource to use in hardware debug. The signal names mentioned in the following
individual sections can be probed using the ChipScope debugging tool for debugging the
specific problems.
General Checks
Ensure that all the timing constraints for the core were properly incorporated from the
example design and that all constraints were met during implementation.
•
Does it work in post-place and route timing simulation? If problems are seen in
hardware but not in timing simulation, this could indicate a PCB issue. Ensure that all
clock sources are active and clean.
•
If using MMCMs in the design, ensure that all MMCMs have obtained lock by
monitoring the LOCKED port.
•
If your outputs go to 0, check your licensing.
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Appendix D
Additional Resources and Legal Notices
Xilinx Resources
For support resources such as Answers, Documentation, Downloads, and Forums, see Xilinx
Support.
References
These documents provide supplemental material useful with this user guide:
1. ISE to Vivado Design Suite Migration Guide (UG911)
2. Vivado Design Suite User Guide: Designing with IP (UG896)
3. Vivado Design Suite User Guide: Programming and Debugging (UG908).
4. Vivado Design Suite User Guide: Getting Started (UG910)
5. Vivado Design Suite User Guide: Logic Simulation (UG900)
6. MMCM and PLL Dynamic Reconfiguration (XAPP888)
7. Vivado Design Suite User Guide: Designing IP Subsystems Using IP Integrator (UG994)
8. UltraScale Architecture Clocking Resources User Guide (UG572)
9. 7 Series FPGAs Clocking Resources User Guide (UG472)
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Appendix D: Additional Resources and Legal Notices
Revision History
The following table shows the revision history for this document.
Date
Version
Revision
04/01/2015
5.1
• Added the Minimum Input frequencies for MMCM and PLL for Virtex-7
devices.
• Added an example describing the reference steps when using the AXI
Interface for using the dynamic reconfiguration interface.
10/01/2014
5.1
Added UltraScale architecture support and User Parameters mapping table.
10/01/2014
5.1
Added UltraScale architecture support and User Parameters mapping table.
04/02/2014
5.1
Updated Configuring Output Clock section. Added Resource utilization for
AXI4-Lite interface using Kintex-7 device.
12/18/2013
5.1
Added UltraScale Architecture support.
10/02/2013
5.1
Updated for to synch doc version with core version. Added Migration
information.
03/20/2013
1.3
Updated for core version, added XCI parameters and Safe Clock Startup
diagrams and waveforms.
12/18/2012
1.2
Updated for core version, Active Low RESET support, and Vivado GUI screens.
10/16/2012
1.1
Updated for core version and Vivado GUI screens.
07/25/2012
1.0
Initial release of Product Guide, replacing DS709 and UG521.
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Clocking Wizard v5.1
PG065 April 1, 2015
www.xilinx.com
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