Silicon Labs C8051F930-DK User's Guide

Silicon Labs C8051F930-DK  User's Guide

C 8 0 5 1 F 9 3 x / 9 2 x C 8 0 5 1 F 9 3 0 D E V E L O P M E N T K I T U S E R ’ S G U I D E

1. Relevant Devices

The C8051F930 Development Kit is intended as a development platform for the microcontrollers in the C8051F93x-C8051F92x MCU family.


1. The target board included in this kit is provided with a pre-soldered C8051F930 MCU (LQFP32 package).

2. Code developed on the C8051F930 can be easily ported to the other members of this MCU family.

3. Refer to the C8051F93x-C8051F92x data sheet for the differences between the members of this MCU family.

2. Kit Contents

The C8051F930 Development Kit contains the following items:  C8051F930 Target Board  C8051Fxxx Development Kit Quick-Start Guide  AC to DC Power Adapter  USB Debug Adapter (USB to Debug Interface)  2 USB Cables  2 AAA Batteries  CD-ROM

Rev 0.7 5/14 Figure 1. C8051F930 Target Board Copyright © 2014 by Silicon Laboratories C8051F93x/92x

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3. Hardware Setup Using a USB Debug Adapter

The target board is connected to a PC running the Silicon Laboratories IDE via the USB Debug Adapter as shown

in Figure 2.

1. Connect the USB Debug Adapter to the DEBUG connector on the target board with the 10-pin ribbon cable.

2. Connect one end of the USB cable to the USB connector on the USB Debug Adapter. 3. Verify that a shorting block is installed on J17 and that SW5 is in the ON position.

4. Connect the other end of the USB cable to a USB Port on the PC.

5. Connect the ac/dc power adapter to power jack P1 on the target board (Optional).


 Use the Reset button in the IDE to reset the target when connected using a USB Debug Adapter.

 Remove power from the target board and the USB Debug Adapter before connecting or disconnecting the ribbon cable from the target board. Connecting or disconnecting the cable when the devices have power can damage the device and/or the USB Debug Adapter.

PC Target Board R15 J16 H1 J15 P1.6







J7 U1 F930 J13 CP 2103 U3 J12 J8 +1VD J11 COIN_CELL AAA_BAT WALL_PWR VBAT J9 J3 J6 VDD/DC+ J5 ` J2 J14 +3VD RESET IMEASURE J17 H2 VBAT OFF ON SW5 J1 P2 SW4 USB Debug Adapter AC/DC Adapter USB Cable

Figure 2. Hardware Setup Using a USB Debug Adapter Rev 0.7

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4. Software Setup

Simplicity Studio greatly reduces development time and complexity with Silicon Labs EFM32 and 8051 MCU products by providing a high-powered IDE, tools for hardware configuration, and links to helpful resources, all in one place.

Once Simplicity Studio is installed, the application itself can be used to install additional software and documentation components to aid in the development and evaluation process.

Figure 3. Simplicity Studio

The following Simplicity Studio components are required for the C8051F930 Development Kit:  8051 Products Part Support  Simplicity Developer Platform Download and install Simplicity Studio from or .

Once installed, run Simplicity Studio by selecting


Silicon Labs

Simplicity Studio

Simplicity Studio

from the start menu or clicking the

Simplicity Studio

shortcut on the desktop. Follow the instructions to install the software and click

Simplicity IDE

to launch the IDE.

The first time the project creation wizard runs, the

Setup Environment

wizard will guide the user through the process of configuring the build tools and SDK selection.

In the

Part Selection

step of the wizard, select from the list of installed parts only the parts to use during development. Choosing parts and families in this step affects the displayed or filtered parts in the later device selection menus. Choose the C8051F93x family by checking the


check box. Modify the part selection at any time by accessing the

Part Management

dialog from the



Simplicity Studio

Part Management

menu item.

Simplicity Studio can detect if certain toolchains are not activated. If the

Licensing Helper

is displayed after completing the

Setup Environment

wizard, follow the instructions to activate the toolchain.

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4.1. Running Blinky

Each project has its own source files, target configuration, SDK configuration, and build configurations such as the




build configurations. The IDE can be used to manage multiple projects in a collection called a workspace. Workspace settings are applied globally to all projects within the workspace. This can include settings such as key bindings, window preferences, and code style and formatting options. Project actions, such as build and debug are context sensitive. For example, the user must select a project in the

Project Explorer

view in order to build that project.

To create a project based on the Blinky example: 1. Click the

Software Examples

tile from the Simplicity Studio home screen.

2. In the


drop-down, select

C8051F930 Development Kit

, in the


drop-down, select


, and in the


drop-down, select the desired SDK. Click



3. Select


and click



4. Under

C8051F930 Development Kit

in the


folder, select

F93x-92x Blinky

and click



5. Click on the project in the

Project Explorer

and click


, the hammer icon in the top bar. Alternatively, go to


Build Project


6. Click


to download the project to the hardware and start a debug session.

7. Press the


button to start the code running. The LED should blink. 8. Press the


button to stop the code.

9. Press the

Reset the device

button to reset the target MCU.

10. Press the


button to return to the development perspective.

4.2. Simplicity Studio Help

Simplicity Studio includes detailed help information and device documentation within the tool. The help contains descriptions for each dialog window. To view the documentation for a dialog, click the question mark icon in the window: This will open a pane specific to the dialog with additional details.

The documentation within the tool can also be viewed by going to


Help Contents





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4.3. Simplicity Configurator

The Simplicity Configurator is a configuration and code generation tool. This utility helps accelerate development by automatically generating initialization source code to configure and enable the on-chip resources needed by most design projects. In just a few steps, the wizard creates complete startup code for a specific Silicon Labs MCU.

To create a new Simplicity Configurator project: 1. Click the

Create new project

link from the welcome screen or go to



Silicon Labs MCU Project


2. In the


drop-down, select

C8051F930 Development Kit



, in the


drop-down, select


, and in the


drop-down, select the desired SDK. Click



3. Select

Simplicity Configurator Program

and click



4. Fill in the

Project name

and select the desired device. The


device is on the C8051F930 Target Board. Click



The Simplicity Configurator project displays properties for each peripheral. To configure a peripheral, click on the

DefaultMode Peripherals

tab at the bottom and click on a peripheral. Checking the box for a peripheral will add it to code generation. Once a peripheral is selected, configure the registers using the


view. Select a new value for a property with either an input box or a drop-down menu and press


to set it.

Figure 4. Simplicity Configurator – Configuring Peripheral Properties Rev 0.7


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To configure pins, click on the

DefaultMode Port I/O

tab at the bottom of main window. Clicking on a pin brings up a property window for the pin. Clicking anywhere else in the main window opens a property window for the crossbar. Select multiple pins with

Ctrl + left click

or mouse dragging over the desired set of pins. The package diagram displays the configured peripherals on the pins, including non-crossbar signals (i.e. ADC inputs).

Code generation updates every time the configuration project saves. After configuring the device, add any non initialization code, build, and debug the same as with any other project.

More information on Simplicity Configurator can be found in

AN0823: Simplicity Configurator User’s Guide


AN0821: Simplicity Studio C8051F85x Walkthrough

. Application notes can be found on .

6 Figure 5. Simplicity Configurator – Configuring Port I/O Rev 0.7

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4.4. CP210x USB to UART VCP Driver Installation

The MCU Card includes a Silicon Labs CP210x USB-to-UART Bridge Controller. Device drivers for the CP210x need to be installed before the PC software can communicate with the MCU through the UART interface. Use the drivers included CD-ROM or download the latest drivers from the website ( ).

1. If using the CD-ROM, the

CP210x Drivers

option will launch the appropriate driver installer. If downloading the driver package from the website, unzip the files to a location and run the appropriate installer for the system (x86 or x64). 2. Accept the license agreement and follow the steps to install the driver on the system. The installer will let you know when your system is up to date. The driver files included in this installation have been certified by Microsoft.

3. To complete the installation process, connect the included USB cable between the host computer and the


USB connector (J5) on the MCU Card. Windows will automatically finish the driver installation. Information windows will pop up from the taskbar to show the installation progress.

4. If needed, the driver files can be uninstalled by selecting the

Windows Driver Package—Silicon Laboratories...

option in the

Programs and Features


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4.5. Silicon Labs Battery Life Estimator

The Battery Life Estimator is a system design tool for battery operated devices. It allows the user to select the type of battery they are using in the system and enter the supply current profile of their application. Using this information, it performs a simulation and provides an estimated system operating time. The Battery Life Estimator

is shown in Figure 6.

Figure 6. Battery Life Estimator Utility

From Figure 6, the two inputs to the Battery Life Estimator are battery type and discharge profile. The utility

includes battery profiles for common battery types such as AAA, AA, A76 Button Cell, and CR2032 coin cell. The discharge profile is application-specific and describes the supply current requirements of the system under various supply voltages and battery configurations. The discharge profile is independent of the selected power source.

Several read-only discharge profiles for common applications are included in the pulldown menu. The user may also create a new profile for their own applications.

To create a new profile: 1. Select the profile that most closely matches the target application or choose the "Custom Profile".

2. Click Manage.

3. Click Duplicate.

4. Click Edit.

Profiles may be edited with the easy-to-use GUI (shown in Figure 7).

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C80 51 F 93 x/9 2x Figure 7. Battery Life Estimator Discharge Profile Editor

The Discharge Profile Editor allows the user to modify the profile name and description. The four text entry boxes on the left hand side of the form allow the user to specify the amount of time the system spends in each power mode. On the right hand side, the user may specify the supply current of the system in each power mode. Since supply current is typically dependent on supply voltage, the discharge profile editor provides two columns for supply current. The V2 and V1 voltages at the top of the two columns specify the voltages at which the current measurements were taken. The Battery Life Estimator creates a linear approximation based on the input data and is able to feed the simulation engine with an approximate supply current demand for every input voltage.

The minimum system operating voltage input field allows the system operating time to stop increasing when the simulated battery voltage drops below a certain threshold. This is primarily to allow operating time estimates for systems that cannot operate down to 1.8 V, which is the voltage of two fully drained single-cell batteries placed in series.

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The wakeup frequency box calculates the period of a single iteration through the four power modes and displays the system wake up frequency. This is typically the "sample rate" in low power analog sensors.

Once the battery type and discharge profile is specified, the user can click the "Simulate" button to start a new simulation. The simulation engine calculates the estimated battery life when using one single-cell battery, two

single-cell batteries in series, and two single-cell batteries in parallel. Figure 8 shows the simulation output window.

Figure 8. Battery Life Estimator Utility Simulation Results Form

The primary outputs of the Battery Life Estimator are an estimated system operating time and a simulated graph of battery voltage vs. time. Additional outputs include estimated battery capacity, average current, self-discharge current, and the ability to export graph data to a comma delimited text file for plotting in an external graphing application.

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5. Target Board

The C8051F930 Development Kit includes a target board with a


device pre-installed for evaluation and preliminary software development. Numerous input/output (I/O) connections are provided to facilitate prototyping

using the target board. Refer to Figure 9 for the locations of the various I/O connectors. Figure 11 on page 13

shows the factory default shorting block positions. P1 P2 P3 J1 J2, J3, J4 J5 J6 J7 J8 J9 J10, J11 J12 J13 J14 J15 J16 J17 H1 H2 SW4 SW5 Expansion connector (96-pin) Power connector (accepts input from 7 to 15 VDC unregulated power adapter) USB connector (connects to PC for serial communication) Enable/Disable VBAT Power LED Port I/O headers (provide access to Port I/O pins) Enable/Disable VDD/DC+ Power LED Provides an easily accessible ground clip Connects pin P0.7 (IREF0 Output) to resistor R14 and capacitor C19 Connects P0.2 and P0.3 to switches and P1.5 and P1.6 to LEDs DEBUG connector for Debug Adapter interface Selects the power supply source (Wall Power, AAA Battery, or Coin Cell) Connects Port I/O to UART0 interface Connects external VREF capacitor to the P0.0/VREF Connects the PCB ground plane to P0.1/AGND Connects negative potentiometer (R14) terminal to pin P1.4 or to GND Connects the potentiometer (R14) wiper to P0.6/CNVSTR Creates an open in the power supply path to allow supply current measurement Analog I/O terminal block Provides terminal block access to the input and output nodes of J17 Switches the device between One-Cell (0.9–1.8 V supply) or Two-Cell (1.8–3.6 V) mode Turns power to the MCU on or off P1 R15 J16 H1 P1.4





SW2 P0.2




Figure 9. C8051F930 Target Board

Pin 1 Pin 2

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The following items are located on the bottom side of the board. See Figure 10.

BT1 Battery Holder for 1.5 V AAA. Use for one-cell or two-cell mode.

BT2 Battery Holder for 1.5 V AAA. Use for two-cell mode only.

BT3 Battery Holder for 3 V Coin Cell (CR2032).

BT4 Battery Holder for 1.5 V Button Cell (A76 or 357).

Note: BT2 is only used in two-cell mode.

NEG POS BT3 (CR2032) BT2 (AAA) POS BT4 (A76 or 357) NEG BT1 (AAA)

Figure 10. Bottom of C8051F930 Target Board 12 Rev 0.7

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5.1. Target Board Shorting Blocks: Factory Defaults

The C8051F930 target board comes from the factory with pre-installed shorting blocks on many headers. Figure 11

shows the positions of the factory default shorting blocks.

P1 R15 J16 H1 P1.4





SW2 P0.2





Figure 11. C8051F930 Target Board Shorting Blocks: Factory Defaults

Pin 1 Pin 2

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5.2. Target Board Power Options and Current Measurement

The C8051F930 Target Board supports three power options, selectable by the three-way header (J10/J11). The power options vary based on the configuration (one-cell or two-cell mode) selected by SW4. Power to the MCU may be switched on/off using the power switch (SW5).

Important Note: The power switch (SW5) must be in the OFF position prior to switching between one-cell and two-cell mode using SW4.

The power options are described in the paragraphs below.

5.2.1. Wall Power

When the J10/J11 three-way header is set to WALL_PWR, the C8051F930 Target Board may be powered from the following power sources:  9 VDC power using the ac to dc power adapter (P2)  5 VDC USB VBUS power from PC via the USB Debug Adapter (J9)  5 VDC USB VBUS power from PC via the CP2103 USB connector (P3) All the three power sources are ORed together using reverse-biased diodes (D1, D2, D3), eliminating the need for headers to choose between the sources. The target board will operate as long as any one of the power sources is present. The ORed power is regulated to a 3.3 V dc voltage using a LDO regulator (U2). The output of the regulator powers the +3 VD net on the target board. If SW4 is configured to select two-cell mode, the VBAT supply net on the target board is powered directly from the +3 VD net. If SW4 is configured to select one-cell mode, the VBAT supply net is powered directly from the +1 VD.

This power supply net takes +3 VD and passes it through a 1.65 V LDO. The LDO’s output voltage is variable and can be set by changing the value of resistor R32.


5.2.2. AAA Battery

When the J10/J11 three-way header is set to AAA_BAT, the C8051F930 Target Board may be powered from a single AAA battery inserted in BT1 or from the series combination of the AAA batteries inserted in BT1 and BT2. A single battery is selected when SW4 is configured to one-cell mode. The two AAA batteries configured in series to provide a voltage of ~3 V are selected when SW4 is configured to two-cell mode.


5.2.3. Coin Cell Battery

When the J10/J11 three-way header is set to COIN_CELL, the C8051F930 Target Board may be powered from a single 1.5 V Alkaline (A76) or Silver Oxide (357) button cell inserted in BT4 or from a single 3 V Lithium (CR2032) coin cell inserted in BT3. The button cell (BT4) is selected when SW4 is configured to one-cell mode, and the coin cell (BT3) is selected when SW4 is configured to two-cell mode.


5.2.4. Measuring Current

The header (J17) and terminal block (H2) provide a way to measure the total supply current flowing from the power supply source to the MCU. The measured current does not include any current from the VBAT LED (DS2), the address latch (U4) or the quiescent current from the power supply; however, it does include the current used by any LEDs powered from the VDD/DC+ supply net or sourced through a GPIO pin. See the target board schematic

in Figure 12 through Figure 14 for additional information.

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5.3. System Clock Sources

5.3.1. Internal Oscillators

The C8051F930 device installed on the target board features a factory calibrated programmable high-frequency internal oscillator (24.5 MHz base frequency, ±2%) and a low power internal oscillator (20 MHz ±10%). After each reset, the low power oscillator divided by 8 results in a default system clock frequency of 2.5 MHz (±10%). The selected system clock and the system clock divider may be configured by software for operation at other frequencies. For low-frequency operation, the C8051F930 features a smaRTClock real time clock. A 32.768 kHz Watch crystal (Y2) is included on the target board. If you wish to operate the C8051F930 device at a frequency not available with the internal oscillators, an external crystal may be used. Refer to the C8051F93x-C8051F92x data sheet for more information on configuring the system clock source.

5.3.2. External Oscillator Options

The target board is designed to facilitate the installation of an external crystal (Y1). Install a 10 M  resistor at R9 and install capacitors at C20 and C21 using values appropriate for the crystal you select. If you wish to operate the external oscillator in capacitor or RC mode, options to install a capacitor or an RC network are also available on the target board. Populate C21 for capacitor mode, and populate R16 and C21 for RC mode. Refer to the C8051F93x C8051F92x data sheet for more information on the use of external oscillators.

5.4. Port I/O Headers (J2, J3, J4, J6)

Access to all Port I/O on the C8051F930 is provided through the headers J2, J3, and J4. The header J6 provides access to the ground plane for easy clipping of oscilloscope probes.

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5.5. Switches and LEDs

Three push-button switches are provided on the target board. Switch SW1 is connected to the reset pin of the C8051F930. Pressing SW1 puts the device into its hardware-reset state. Switches SW2 and SW3 are connected to the C8051F930’s general purpose I/O (GPIO) pins through headers. Pressing SW2 or SW3 generates a logic low signal on the port pin. Remove the shorting block from the header (J8) to disconnect the switches from the port

pins. The port pin signal is also routed to pins on the J2 and P1 I/O connectors. See Table 1 for the port pins and

headers corresponding to each switch.

Two touch sensitive (contactless) switches are provided on the target board. The operation of these switches require appropriate firmware running on the C8051F930 MCU that can sense the state of the switch.

Five power LEDs are provided on the target board to serve as indicators. Each of the two regulators has a red LED used to indicate the presence of power at the output of the regulator. A red USB Power LED turns on when a USB cable is plugged into the USB connector P3. One power LED is also added to each of the two primary supply nets powering the MCU (VDD/DC+ and VBAT). The LEDs connected to the supply nets may be disabled by removing the shorting blocks from J1 and J5.

Two LEDs are connected to GPIO pins P1.5 and P1.6 for use by application software. See Table 1 for the port pins

and headers corresponding to each LED.

A potentiometer (R15) is also provided on the target board for generating analog signals. Place a shorting block on J16 to connect the wiper to P0.6/CNVSTR. The header J15 allows the negative terminal of the potentiometer to be tied to GND or to P1.4. When tied to GND, the potentiometer is always enabled and will draw a measurable amount of supply current. When tied to P1.4, it only draws current when P1.4 is driving a logic 0 and draws no current when P1.4 is driving a logic 1.

Table 1. Target Board I/O Descriptions Description

SW1 SW2 SW3 P2.0 (Touch Sense Switch) P2.1 (Touch Sense Switch) Red LED (P1.5) Yellow LED (P1.6) Red LED (VDD/DC+) Red LED (VBAT) Red LED (USB Power) Red LED (+1 VD Power) Red LED (+3 VD Power) Potentiometer (R15)


Reset P0.2






VDD/DC+ Supply Net VBAT Supply Net USB VBUS +1 VD Regulator Output +3 VD Regulator Output P0.6/P1.4


none J8[5–6] J8[7–8] none none J8[1–2] J8[3–4] J5 J1 none none none J15, J16

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5.6. Expansion I/O Connector (P1)

The 96-pin Expansion I/O connector P1 provides access to all signal pins of the C8051F930 device (except the C2 debug interface signals). In addition, power supply and ground pins are included. A small through-hole prototyping

area is also provided. See Table 2 for a list of pin descriptions for P1.

Row A Pin #

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 29 30 31 32 21 22 23 24 25 26 27 28


+3 VD nc nc nc nc nc nc nc nc nc P0.5/RX P0.2H

P1.7/AD7 P1.4/AD4 P1.1/AD1 A6-Latch A3-Latch A0-Latch nc P2.2/A10 /WR P2.3/A11 P2.0/A8 nc nc GND nc nc nc nc nc nc

Table 2. P1 Pin Descriptions Row B Pin #

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 29 30 31 32 21 22 23 24 25 26 27 28


GND nc nc nc nc nc nc nc nc P0.7/IREF0 P0.4/TX P0.1/AGND P1.6/AD6 P1.3/AD3 P1.0/AD0 A5-Latch A2-Latch P2.3/A11 nc P2.1/A9 /RD P2.2/A10 ALE nc GND nc nc VDD/DC+ nc nc nc GND

Row C Pin #

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 29 30 31 32 21 22 23 24 25 26 27 28


nc nc nc nc nc nc nc nc nc P0.6/CNVSTR P0.3H

P0.0/VREF P1.5/AD5 P1.2/AD2 A7-Latch A4-Latch A1-Latch nc P2.3/A11 P2.0/A8 P0.2H

P2.1/A9 nc nc nc nc nc VBAT nc nc nc nc

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5.7. Target Board DEBUG Interface (J9)

The DEBUG connector J9 provides access to the DEBUG (C2) pins of the C8051F930. It is used to connect the Serial Adapter or the USB Debug Adapter to the target board for in-circuit debugging and Flash programming.

Table 3 shows the DEBUG pin definitions.

Table 3. DEBUG Connector Pin Descriptions Pin #

1 2, 3, 9 4 5 6 7 8 10


+3 VD (+3.3 VDC) GND (Ground) P2.7/C2D RST (Reset) P2.7

RST/C2CK Not Connected USB Power (+5 VDC from J9)

5.8. Serial Interface (J12)

A USB-to-UART bridge circuit (U3) and USB connector (P3) are provided on the target board to facilitate serial connections to UART0 of the C8051F930. The Silicon Labs CP2103 (U3) USB-to-UART bridge provides data connectivity between the C8051F930 and the PC via a USB port. The VIO power supply and TX, RX, RTS and CTS signals of UART0 may be connected to the CP2103 by installing shorting blocks on header J12. The shorting

block positions for connecting each of these signals to the CP2103 are listed in Table 4. To use this interface, the

USB-to-UART device drivers should be installed as described in Section 4.4. "CP210x USB to UART VCP Driver Installation‚" on page 7.

Table 4. Serial Interface Header (J12) Description Header Pins UART0 Pin Description

J12[9–10] J12[7–8] J12[5–6] J12[3–4] J12[1–2] CP2103_VIO (VDD/DC+) TX_MCU (P0.5) RX_MCU (P0.4) RTS (P0.6) CTS (P0.7)

5.9. Analog I/O (H1)

Several of the C8051F930 target device’s port pins are connected to the H1 terminal block. Refer to Table 5 for the

H1 terminal block connections.

Table 5. H1 Terminal Block Pin Descriptions Pin #

1 2 3 4


P0.6/CNVSTR P0.7/IREF0 GND (Ground) P0.0/V REF (Voltage Reference)

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5.10. IREF Connector (J7)

The C8051F930 Target Board also features a current-to-voltage 1 k  load resistor that may be connected to the current reference (IREF0) output that can be enabled on port pin (P0.7). Install a shorting block on J7 to connect port pin P0.7 of the target device to the load resistor. If enabled by software, the IREF0 signal is then routed to the J2[8] and H1[2] connectors.

5.11. VREF and AGND Connector (J13, J14)

The C8051F930 Target Board also features 4.7 µF capacitor in parallel with a 0.1 µF that can be connected to P0.0/VREF when using the Precision Voltage Reference. The capacitors are connected to P0.0/VREF when a shorting block is installed on J13. Using the Precision Voltage Reference is optional since 'F93x-'F92x devices have an on-chip High-Speed Voltage Reference. The shorting block J14 allows P0.1/AGND to be connected to ground. This provides a noise-free ground reference to the analog-to-digital Converter. The use of this dedicated analog ground is optional.

5.12. C2 Pin Sharing

On the C8051F930, the debug pins C2CK and C2D are shared with the pins RST and P2.7, respectively. The target board includes the resistors necessary to enable pin sharing which allow the RST and P2.7 pins to be used normally while simultaneously debugging the device. See Application Note “AN124: Pin Sharing Techniques for the C2 Interface” at

for more information regarding pin sharing.

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6. Frequently Asked Questions


Should power be turned off when switching between one-cell and two-cell mode?

Yes, power must be turned off by placing SW5 in the OFF position when switching between one-cell and two-cell mode. Switching between modes while power is on may result in increased power consumption and possible damage to low voltage transistors. 2.

I have placed the MCU in Sleep Mode. Why is the supply current greater than 1 µA?

This can be caused by a number of factors. Check the following: a. Verify that the USB Debug Adapter is not connected to the device. When connected, it can draw approximately 2–5 µA from the VDD/DC+ supply net.

b. Verify that the P1.5 and P1.6 LEDs are turned off in software (P1.5 and P1.6 set to logic HIGH). Alternatively, the P1.5 and P1.6 LEDs can be disabled by removing the corresponding shorting blocks from J8.

c. Verify that the VDD/DC+ Power LED is disabled (remove shorting block from J5). d. Verify that the shorting block on J15 does not connect the potentiometer negative terminal to GND, since this would result in continuous current of ~ 300 µA. The shorting block may be removed, or configured to enable the potentiometer when P1.4 is set to logic LOW. When the potentiometer enable is under software control, be sure to set P1.4 to logic HIGH prior to placing the device in Sleep Mode.

e. Verify that J7, J13, and J14 do not have shorting blocks installed.


I have been measuring the sleep mode current using the “µA” setting on my multimeter. Why am I no longer able to connect to the IDE?

When most multimeters are placed in “µA” mode, a large resistance is placed in series with the power supply. This “current limiting” resistor prevents the MCU from starting up. To measure current during startup, make sure that the multimeter is configured to its “mA” setting. Alternatively, a shorting block can be placed on J17 to ensure that the multimeter does not limit current during startup.


Where can I find a schematic of the C8051F930 Target Board?

A target board schematic can be found in the C8051F930-DK User’s Guide which is available on the Development Tools CD and is installed in the following folder (by default): C:\SiLabs\MCU\Documentation\UsersGuides 5.

Which power LED should I use to determine if the MCU is powered?

The VDD/DC+ LED (DS5) should be used to determine if the MCU is powered. If you have applied power to the board, but the VDD/DC+ LED is not turning on, check the following: a. Verify that the correct power source (J10, J11) is selected. b. Verify that J17 has a shorting block.

c. Verify that SW5 is in the ON position.

d. Verify that J5 has a shorting block installed.

20 Rev 0.7

C80 51 F 93 x/9 2x


What can I do to reduce active supply current?

Below are some suggestions for reducing the active supply current: a. Clear all wake-up sources in the PCU0CF register. This will allow the low power oscillator to be disabled when it is not being used as the system clock. This optimization can reduce the supply current by up to 30 µA.

b. When operating at system clock frequencies above 10 MHz, minimize supply current by setting the BYPASS bit (FLSCL.6) to 1. If the system clock needs to decrease below 10 MHz, clear the BYPASS bit to 0.

c. If the precision oscillator is not being used, turn off the precision oscillator bias by setting the OSCBIAS bit (REG0CN.4) to 0.


Why does P0.7/IREF0 have a voltage of 200 mV when IREF0CN is set to 0x00?

When IREF0CN is set to 0x00, the current reference is completely turned off. When a shorting block is installed on J7, the voltage at P0.7/IREF0 should be 0 V unless one of the following conditions is present: a. The P0.7/IREF0 pin is not configured for analog I/O (weak pull-up enabled).

b. The P0.7/IREF0 pin is being used as CTS (a shorting block is installed on J12).

8. I have configured a Port pin as an analog input. Why is it still shorted to ground?

On C8051F93x-C8051F92x devices, configuring a Port pin to analog mode (using PnMDIN) disables the digital input path and the weak pull-up. It does not explicitly disable the output drivers. Software can ensure that the output drivers are disabled by configuring the Port pin to open-drain output mode (using PnMDOUT) and writing 1 to the port latch. 9.

Why does power consumption increase when an analog signal (hovering around mid-supply) is connected to a digital input?

This phenomenon is called the “crowbar” effect and is present in all CMOS circuitry. If the input of a CMOS structure is not a strong 1 or 0, then both the PMOS and NMOS devices are partially turned on causing current flow from VDD to GND. To prevent the “crowbar” effect, ensure that pins with analog voltage levels are configured for analog I/O. 10.

Why does the dc/dc converter stop regulating when the load current exceeds 10 mA?

The default register settings for the dc/dc converter are optimized for low power applications requiring less than 10 mA of supply current. If the application requires additional supply current, the default values may be overridden to provide up to 65 mW of output power.

To configure the dc/dc converter to high power mode, perform the following steps prior to enabling any high power device: a. Set DC0CN = 0x01. This selects the high-current switches.

b. Set DC0CF = 0x04. This sets the peak inductor current limit to 500 mA.

Rev 0.7


C 8 0 5 1 F 9 3 x / 9 2 x


When the missing clock detector is enabled, why does the MCU reset if I switch from the default system clock (Low Power Oscillator divided by 8) to smaRTClock divided by 1?

Background: —The missing clock detector will trigger a reset if the system clock period exceeds 100 µs.

—Switchover between clock sources occurs in 1 clock cycle of the slowest clock.

—Changing the clock divide value requires up to 128 cycles of the undivided clock source.

Since the

clock source

change occurs in a single cycle and the

clock divide

change can take up to 128 cycles, the system clock will be set to the

new clock source divided by the old divide value

for a brief period of time. In this example, the actual system clock will be 4.096 kHz for up to 128 cycles of the undivided clock source. This causes the missing clock detector to time out and reset the MCU.

The proper way of changing the system clock when both the

clock source

and the

clock divide

value are being changed is as follows: If switching from a fast “undivided” clock to a slower “undivided” clock: a. Change the

clock divide


b. Poll for CLKRDY > 1.

c. Change the

clock source


If switching from a fast “undivided” clock to a slower “undivided” clock: d. Change the

clock source


e. Change the

clock divide


f. Poll for CLKRDY > 1.

12. Why is the MCU prematurely released from reset when using a wall supply with a slow rise time?

The maximum VDD Ramp Time is specified at 3 ms. If the power supply ramp takes longer than 3 ms to reach 0.9 V, then the device may be released from reset before the supply has reached the minimum operating voltage. The slow ramp time (>3 ms) can occur when using a bench power supply that does not have an output enable switch.

22 Rev 0.7

7. Schematics

C80 51 F 93 x/9 2x Rev 0.7


C 8 0 5 1 F 9 3 x / 9 2 x 24 Rev 0.7

C80 51 F 93 x/9 2x Rev 0.7


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