Texas Instruments | Interfacing the TLC5510 Analog-to-Digital Converter to the TMS320C203 DSP | Application notes | Texas Instruments Interfacing the TLC5510 Analog-to-Digital Converter to the TMS320C203 DSP Application notes

Texas Instruments Interfacing the TLC5510 Analog-to-Digital Converter to the TMS320C203 DSP Application notes
Interfacing the TLC5510
Analog to Digital Converter
to the TMS320C203 DSP
APPLICATION REPORT: SLAA029
Perry Miller
Advanced Analog Products
Advanced Analog Applications Group
Digital Signal Processing Solutions
March 1998
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CONTACT INFORMATION
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Contents
Abstract ......................................................................................................................... 7
Product Support ........................................................................................................... 8
Related Documentation............................................................................................. 8
World Wide Web ....................................................................................................... 8
Introduction................................................................................................................... 9
TLC5510 ADC Overview ............................................................................................. 11
TLC5510 EVM ........................................................................................................ 11
Supply Voltages .............................................................................................. 13
Analog Input.................................................................................................... 13
TLC5510 EVM to TMS320C203 DVM Interfacing Signals ....................................... 16
Software Overview...................................................................................................... 19
Appendix A. Program Listing.................................................................................... 21
Figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
TLC5510 to TMS320C203 Interface Block Diagram.......................................... 9
TLC5510 I/O Timing Diagram ......................................................................... 10
TLC5510 Functional Block Diagram................................................................ 11
TLC5510 EVM Circuit Diagram ....................................................................... 12
TLC5510 EVM toTMS320C203 DVM Interface Schematic.............................. 18
TLC5510 to TMS320C203 Interface Program Flow Chart ............................... 20
Tables
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
TLC5510 Parameters...................................................................................... 10
TLC5510 Supply Voltages .............................................................................. 13
DC and AC Coupling Connections to J4 Input................................................. 14
Jumper Configuration and Voltage Conversion Range.................................... 15
Signals Monitored by Test Points.................................................................... 15
Interfacing the TLC5510 Analog to
Digital Converter to the TMS320C203
DSP
Abstract
This application report presents guidelines for interfacing the
Texas Instruments (TI) TLC5510 8-bit parallel-output analog-todigital converter (ADC) to the TI TMS320C203 DSP data bus. The
8-bit ADC operates at a rate of 20 MHz. The C callable application
program (assembly code) used to initialize the TMS320C203 and
execute the code is also discussed.
This report serves as reference information for further
development of hardware and software. The contents include
hardware schematics and associated program software, block and
timing diagrams, and a program flow chart.
Interfacing the TLC5510 Analog to Digital Converter to the TMS320C203 DSP
7
SLAA029
Product Support
Related Documentation
The following list specifies product names, part numbers, and
literature numbers of reference documents:
❑
TMS320C2xx User’s Guide, Literature number SPRU127B
❑
TMS3200C1x/C2x/C2xx/C5x Assembly Language Tools,
User’s Guide, Literature number SPRU018D
❑
TI C2xx Development System User’s Manual, from Wyle
Electronics, http://www.wyle.com
‰
‰
‰
‰
‰
‰
‰
TLC5540/TLC5510 Evaluation Module, Literature number
SLAU007
Texas Instruments, Data Book: Data Acquisition Circuits, Data
Conversion, and DSP Analog Conversion Interface, Literature
number SLAD001
Texas Instruments, Data Sheet: TLC5510, TLC5510A 8-Bit
High-Speed Analog-to-Digital Converters, Literature number
SLAS095I
Texas Instruments, Data Sheet: 74AC11004 Hex Converter,
Literature number SCAS033B
Texas Instruments, Data Sheet: TMS320C203, TMS320C209,
TMS320LC203 Digital Signal Processors, Literature number
SPRS025
Texas Instruments, Data Sheet: 74AHCT1G04 Single Inverter
Gate, Literature number SCLS319E
Texas Instruments, Data Sheet: 74AHC1G32 Single 2-Input
Positive-OR Gate, Literature number SCLS317G
World Wide Web
Our World Wide Web site at www.ti.com contains the most up to
date product information, revisions, and additions. Users
registering with TI&ME can build custom information pages and
receive new product updates automatically via email.
8
Interfacing the TLC5510 Analog to Digital Converter to the TMS320C203 DSP
SLAA029
Introduction
The TLC5510 ADC translates the analog input signal into a binary
digital form for data processing. Generally, parallel ADCs are used
for high-speed applications, for example, video frequencies (>5
MHz). However, there is often a trade off between the converter
maximum sampling frequency and its resolution. High-speed
untrimmed ADCs used for video and higher frequencies have
resolutions from 6 to 10 bits. The devices are usually designed
with modified flash architectures producing the most cost-effective
device solution for fabrication.
This application report focuses on the hardware interface and
assembly code implementation. First, the TLC5510 Evaluation
Module (EVM) is reviewed. A detailed discussion of the
TMS320C203 Development Module (DVM) interface to the
TLC5510 EVM follows. Finally, an overview of the software is
presented.
Figure 1 shows a cost-effective solution consisting of a fixed point
TMS320C203 DSP device, a TLC5510 ADC, and control logic
circuits to access the data bus.
Figure 1. TLC5510 to TMS320C203 Interface Block Diagram
TLC5510 EVM
TMS320C203 DVM
[D1:D8]
[D0:D7]
CLOCK IN
CLKOUTI
15
OE
A11
IS
GND
GND
Interfacing the TLC5510 Analog to Digital Converter to the TMS320C203 DSP
9
SLAA029
Figure 2 shows the idealized TLC5510 I/O timing waveforms.
Figure 2. TLC5510 I/O Timing Diagram
The digital data is valid after a delay time tpd = 30 ns for the
TLC5510. Table 1 summarizes important TLC5510 parameters.
Table 1. TLC5510 Parameters
Parameter
MIN
Pulse duration, clock high, tW(H)
Pulse duration, clock low, tW(L)
Parameter
NOM
MAX
UNIT
25
ns
25
ns
20
MSPS
Test Conditions
fconv
Maximum conversion rate
VI(ANLG) = 0.5 V – 2.5 V
BW
Analog input bandwidth
At –1 dB
14
MHz
At –3 dB
23
MHz
CL ≤ 10 pF
18
tdd
Note:
10
Delay time, digital output
30
ns
The following conditions apply: VDD = 5 V, VRT = 2.5 V, VRB = 0.5 V, fs = 20 MSPS, T A = 25°C
Interfacing the TLC5510 Analog to Digital Converter to the TMS320C203 DSP
SLAA029
TLC5510 ADC Overview
The TLC5510 is a CMOS, 8-bit, 20 MSPS (mega samples per
second) ADC utilizing a semi-flash architecture. The TLC5510
ADC includes internal reference resistors, a sample and hold
circuit, and 8-bit parallel outputs with high impedance mode. The
ADC typically consumes 128 mW of power and operates with a
single 5 V supply.
Figure 3 shows the TLC5510 ADC block diagram and the input
and output signals.
Figure 3. TLC5510 Functional Block Diagram
TLC5510 EVM
The Texas Instruments TLC5510 evaluation module (EVM) is
designed specifically for the development of hardware utilizing the
8-bit high-speed low cost TLC5510 ADC.
The ADC is capable of 20 MSPS with an error of just ½ LSB and
typical analog input bandwidth >14 MHz. Above 1 or 2 MHz
sampling rate, the board layout is critical to the performance of the
ADC and requires careful consideration of several issues.
Therefore, using a breadboard for an ADC evaluation is no longer
a suitable method. Figure 4 shows the TLC5510 EVM board
schematic.
Interfacing the TLC5510 Analog to Digital Converter to the TMS320C203 DSP
11
SLAA029
Figure 4. TLC5510 EVM Circuit Diagram
-
12
Interfacing the TLC5510 Analog to Digital Converter to the TMS320C203 DSP
SLAA029
Supply Voltages
For best performance, the TLC5510 EVM board must be provided
with the following three (3) separate voltages:
‰
‰
‰
Analog +5V
Analog -5V
Digital +5V
Table 2 details the jumpers and applications for the supply
voltages.
Table 2. TLC5510 Supply Voltages
Voltage
Jumper
Application
+5V
J2
-5V
+5V
J3
J8
Analog supply voltage and +ve supply of the
input op amp
-ve supply voltage of the input op amp
Digital logic supply voltage
The TLC5510 EVM board has a common analog ground area
(0 V) for the analog +/- 5V supply voltages. The digital ground
area for the digital supply voltage is isolated from analog ground
to prevent noise spikes from the digital logic from influencing the
analog circuits on the board.
The analog and digital grounds can be connected together by
making a connection from E21 to E22 or E13 to E14 (see
Figure 4). With this arrangement, it is possible to create and
evaluate alternative methods of grounding.
Analog Input
Interfacing to the TLC5510 EVM with an analog signal source is
simple because the analog input signal is taken via the BNC
connector J4. This signal is taken to the input of the TLC5510 via
one of four (4) alternative routes:
‰
‰
‰
‰
Direct
Via the amplifier input with DC coupling
Via the amplifier input with AC coupling
User-defined input
Interfacing the TLC5510 Analog to Digital Converter to the TMS320C203 DSP
13
SLAA029
Direct Input
The input signal can be directly fed to the ANALOG IN pin of the
TLC5510 device by jumpering E7 to E8 and E23 to E12. In the
circuit shown in Figure 4, the reference voltage for the TLC5510
ADC is generated by the device internal resistors. If the jumper J6
is inserted, the reference voltage will be 2.28 V with respect to
0 V; otherwise, it will be 2.6 V with respect to 0.6 V.
DC Coupled Amplifier Input
The TLC5510 EVM board input stage uses an AD8001
operational amplifier. With a gain of +2, the amplifier –3dB
bandwidth is 400 MHz. This op amp is suitable for driving the ADC
because it has low distortion and fast settling time.
The amplifier gain is set to +2 by resistor R6 and R8. Removing
R6 sets the gain to +1 (unity gain). The AD8001 is a current
feedback transimpedance amplifier device. The non-inverting
input is at high impedance and the inverting input is at low
impedance; hence, there is a good possibility that the device will
oscillate when R6 is removed from the circuit. To avoid oscillation
at unity gain (+1), R8 must be retained in the circuit and its value
changed to 953 Ω.
Capacitor C14 and resistor R4 are used for antialiasing low-pass
filtering of the op amp output. Frequencies above 10 MHz (fs/2)
are filtered out when C14 = 150 pF and R4 = 49.9 Ω.
Having resistor R4 in series with the output of the op amp helps
reduce the capacitive loading at the output. Resistor R7 prevents
capacitive loading at the test point TP2 by an oscilloscope probe
used for making measurements.
The AD8001 output is connected to the ANALOG IN pin of the
TLC5510 by a jumper wire connecting E10 to E12. The amplifier
input can be DC or AC coupled to the input at J4. Table 3 lists the
connections needed for these options.
Table 3. DC and AC Coupling Connections to J4 Input
14
Input Coupling
Jumper Connection
DC
AC
E3 to E4
E1 to E2
Interfacing the TLC5510 Analog to Digital Converter to the TMS320C203 DSP
SLAA029
AC Coupled Amplifier Input
For an AC coupled input signal, resistor R2 provides voltage
offset. The offset voltage range is 0 V to +5 V (analog). With an
amplifier gain of +2, the positive dynamic output range of the op
amp is reached with an offset value of 2.5 V.
The cutoff frequency of the input low-pass filter is set by C6
(4.7 uF) and resistance value set by potentiometer R2.
TLC5510 Analog Input Range
The permissible analog-input voltage range of the TLC5510
depends on jumper J6 settings. The way in which the jumper
configuration affects the voltage conversion range is illustrated in
Table 4. For example, when jumper J6 is inserted, analog inputs
≥ 2.28 V produces all 1s at the ADC output, and ≤ 0 V analog
input produce all 0s at the converter output.
Table 4. Jumper Configuration and Voltage Conversion Range
Jumper J6
Input Voltage Range
Not inserted
Inserted
0.6V to 2.6V
0V to 2.28V
See the Texas Instruments data sheet, TLC5510, TLC5510A 8-Bit
High-Speed Analog-to-Digital Converters, for information about
other voltage settings.
Test Points
The analog output voltage of the AD8001 op amp is measured at
test points TP1 and TP2 (see Figure 4). Table 5 lists the signals
monitored by each test point.
Table 5. Signals Monitored by Test Points
Test Point
Signal
TP1
Analog ground
TP2
Output of the op amp
Input Defined by the User
If it is necessary to bypass the AD8001 op amp and directly feed
the analog input signal into the TLC5510 ADC, jumper E7 to E8
and jumper E23 to E12 need to be inserted.
Interfacing the TLC5510 Analog to Digital Converter to the TMS320C203 DSP
15
SLAA029
ADC Digital Data Output
The digital data of the TLC5510 ADC is buffered by an octal Dtype latch (SN74AC573). A 22 Ω resistor is placed in series with
Q1 through Q8 outputs to minimize ringing. The individual data
lines are taken to the connection strip J5. The OE pin of the
SN74AC573 latch controls the interface access to the
TMS320C203 data bus.
The jumper between E17 and E18 must be removed and the
outputs of SN74AC573 controlled by means of J5-24 on the
connecting strip (see Figure 4). The outputs are then only active
when the DSP addresses the ADC during data access.
Clock Buffer Circuit
The maximum conversion rate of the TLC5510 ADC is 20 MHz.
The 20 MHz clock signal is fed in via the BNC input J1. It is
buffered by two (2) 74AC11004 inverters before it is applied to
both the clock pin of the TLC5510 and J5-22.
TLC5510 EVM to TMS320C203 DVM Interfacing Signals
An outline schematic of the TLC5510 EVM interface to the Wyle TI
TMS320C203 DVM is shown in Figure 6. The TMS320C203 DVM
is a standalone board carrying a TMS320C203PZ DSP, analog
interface circuit (AIC), flash memory, SRAM, and serial interface
for communication with a PC via the serial COM port.
The fixed point TMS320C203PZ has an instruction cycle time of
50 ns and is optimized for the efficient implementation of digital
signal processing algorithms. Referring to Figure 6, the data bus,
D1 – D8, is connected via the data bus driver SN74AC573 (J5
pins 2,4,6,8,10,12,14, and 16) through a short ribbon cable to the
TMS320C203 DSP data bus lines (D0 – D7).
To prevent bus contention, the SN74AC573 device must only be
in an active state when data is being read from the ADC.
Each time the DSP wishes to read data from the ADC, address
line A11 is set to a logic high level and IS is set to logic low. A11
and IS form the inputs to the control logic that drives the OE pin
to logic low and thus switches the data bus driver SN74AC573
from tristate to an active state.
16
Interfacing the TLC5510 Analog to Digital Converter to the TMS320C203 DSP
SLAA029
The ADC 20 MHz sampling frequency is generated by the DSP,
which outputs the 20 MHz signal at CLKOUT1 pin. The CLKOUT1
signal is connected directly to the BNC input J1 of the TLC5510
EVM. A pair of 74AC11004 inverters buffers the clock before it is
taken to both the ADC and the connecting strip J5-22.
Interfacing the TLC5510 Analog to Digital Converter to the TMS320C203 DSP
17
SLAA029
Figure 5. TLC5510 EVM toTMS320C203 DVM Interface Schematic
-
18
Interfacing the TLC5510 Analog to Digital Converter to the TMS320C203 DSP
SLAA029
Software Overview
The program editing and assembly are done on the host PC and
downloaded to the TMS320C203 DVM for real time processing.
The DSP executes the interface program and acquires and
processes n input samples from the ADC. Figure 6 shows the
program flowchart.
The Crystal is 40 MHz. The internal CPU CLK for the C203 DSP is
20 MHz. CLK IN for the TLC5510 is driven by CLKOUT1, which is
20 MHz.
The program starts with a common initialization procedure for the
DSP followed by the initialization of several auxiliary registers
(ARs).
The following steps define the program constants:
1) Set the data page pointer to 0h.
2) Set Starting Address.
3) Set number of samples.
4) Set A/D address.
The program executes the following steps:
1) On interrupt, disable global interrupts and save PC, ARs, and
Status Registers.
2) Initialize the C203 DSP.
3) Load the appropriate ARs.
4) Send the device address to the TLC5510, loading the A/D
output into the memory
5) After obtaining a predefined number of A/D converter samples,
the DSP exits the “loop” subroutine.
6) Restore the PC, Status Registers, and ARs.
7) Enable global interrupts.
The data is now available for use in customer-defined functions
(algorithms).
Interfacing the TLC5510 Analog to Digital Converter to the TMS320C203 DSP
19
SLAA029
Figure 6. TLC5510 to TMS320C203 Interface Program Flow Chart
START
SET dma POINTER
SET A/D ADDR
SET SAMPLE COUNTER = n
CONTEXT SAVE RET ADDR,
AR1, AR0, ST1, AND ST0
INTIALIZE DSP
LOAD NEW VALUES IN
ARs AND ARP
GENERATE A/D ADDR
PROCESS RECEIVED DATA
NO
# OF A/D SAMPLES
READ = n?
YES
CONTEXT RESTORE
ST1, ST0, AR1, AR0,
AND RET ADDR
ENABLE INTERRUPTS
FUNCTION
END
20
Interfacing the TLC5510 Analog to Digital Converter to the TMS320C203 DSP
SLAA029
Appendix A. Program Listing
***************************************************************************
˝
* (C) TEXAS INSTRUMENTS, INC., 1997
*
˝
* File: TLC5510.ASM
*
* Interface 'C203 Wyle C2xx DSP Development Board to the TLC5510
*
***************************************************************************
; This routine allows the TMS320C203 DSK+ to interface with the TLC5510
; on the external data bus of the DSP. The TLC5510 is a CMOS, 8-bit,
; 20 MSPS analog-to-digital converter(ADC) that utilizes a semiflash
; architecture and operates with a single 5V supply.
;
;
.length 55
.width 80
; Page length = 55 lines
; Page width = 80 characters
.title "TLC5510EVM Interface"
.mmregs
; Include C2xx memory-mapped
registers.
*
* Variables
*
ADC_Addr
.set
0800h
;
;
;
;
;
;
Define octal latch SN74AC573 output
enable(OEn) control bit. Address bit
A11 is gated with IS\ and STRB\ to
formed the OE\ input signal. The
digital data [D1:D8] from the ADC
are buffered by the SN74AC573.
;
Mem_Pointer
.set
0F00h
Sample_Count
.set
001Eh
;
;
;
;
Define starting address in data
memory.
Define the number of analogue input
samples read into data memory.
.ps
B
0
CLRC
RET
CLRC
RET
CLRC
RET
_TLC5510
INTM
; Reset vector-jump to label _TLC5510
; on reset.
; 2h INT1, external interrupt.
INTM
; 4h INT2/INT3, external interrupt.
INTM
; 6h TINT, external interrupt.
.def _TLC5510
locals
.set 0
;
;
;
;
Comment this line out when using
Wyle TASM
Set equal to the number of local
variables.
.ps 1000h
.entry
*
* Our program begins at address 1000h
*
_TLC5510:
;
;Context save
POPD *+
; Save return address
Interfacing the TLC5510 Analog to Digital Converter to the TMS320C203 DSP
21
SLAA029
SAR AR0, *+
SAR AR1, *
LAR AR0, *+, AR1
ADRK locals
SST #1, *+
SST #0, *+
;Save is complete
;
*
*Initialisation
*
;
LAR AR2, #ADC_Addr
LAR AR3, #Mem_Pointer
LAR
MAR
;
;
;
;
Save FP
Save SP
Set-up new FP
Set-up new SP for local variables
; Save status registers
;
; Address for A/D converter, set A11
; Pointer to data memory for conv.
; values
AR4, #(Sample_Count-1); Counter for the number of samples
*, AR3
; Select AR3.
*
* Transfer ADC data
*
;
W_LOOP:
IN *+, ADC_Addr, AR4
; Save each read A/D converter sample
; in data memory.
Banz W_LOOP, *-, AR3
; Loop for n = sample_count-1
**************************************************************************
*
Stack Management on Exit
*
**************************************************************************
; Context restore
MAR *, AR1
; Set ARP = SP
MAR *; Point to saved ST0
LST #0, *; Restore ST0
LST #1, *
; Restore ST1 and ARP
LAR AR1, *; Pop old SP
LAR AR0, *; Pop FP
PSHD *
; Put return address on H/W stack
CLRC INTM
; Enable interrupts
RET
.END
22
; Assembler module end directive
; -optional.
Interfacing the TLC5510 Analog to Digital Converter to the TMS320C203 DSP
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