Silicon Laboratories C8051F960, Руководство пользователя

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5.2. Push-Button Switches and LEDs (SW1–SW4, LED1–LED4)
The UDP C8051F960/Si1020 MCU Card with EMIF has four push-button switches. The four switches connect to
P3.0 through P3.3. The switches are normally open and pull the pin voltage to ground when pressed.
Port pins P3.0 through P3.3 also connect to four LEDs: LED1 through LED4. The LEDs connect to VIO through a
current limiting resistor.
This multiplexing arrangement reduces the number of port pins used from eight to four. Firmware may easily use
either the LED or the switch for each port pin. When using both the LED and the switch on the same port pin,
firmware must momentarily toggle off the LED by writing a 1 to the pin’s port latch to read the push-button switch
status.
5.3. VBAT Selection Switch (SW5)
The UDP C8051F960/Si1020 MCU Card with EMIF has many power options. The VBAT selector switch (SW5)
selects the power source for the main C8051F960/Si1020 VBAT supply pin.
The center VREG position selects the output of the on-board 3.3 V regulator (U1). This is the primary supply option
for development. The on-board regulator has multiple 5 V and 9 V power sources connected via Schottky diodes to
the regulator input. The highest voltage power source will supply power to the regulator.
The power sources for the on-board regulator (U1) are as follows:
 9 V DC Wall Adapter power receptacle (P1).
 Mini-B USB receptacle (J17).
 10-pin Debug connector (J13).
 UDP mothe5 V (when connected).
The BATT position selects the ultra long life 3.6 V lithium thionyl chloride battery (BT1). This battery is a typical
power source for metering applications. The on-board regulator should be used primarily for development because
the battery has a limited peak current capacity.
The UDP position on the VBAT selector selects the UDP motherboard programmable supply (PWR_VDD_OUT) as
the power source for the UPPI Pico Board. Use this position when using the programmable power supply under
software control.
The UDP motherboard can also provide power to the on-board regulator. The VREG position will always work with
the motherboard, while the UDP switch position requires some motherboard configuration. The UDP motherboard
User’s Guide contains additional information.
The VBAT voltage and ground are available on test points in the top-left corner of the MCU card. Use these test
points to power the board from an external lab power supply. When using a lab supply, the VBAT selector switch
should be in the BATT position with the battery removed.
5.4. Debug Header (J13)
The standard 10-pin debug header supports the Silicon Labs USB Debug Adapter. This connector provides a C2
debug connection to C8051F960/Si1020 on the UPPI Pico Board. The USB Debug Adapter supports two types of
debug connections: C2 and JTAG. When using this MCU card with the Silicon Labs IDE, select C2 in the
connection options dialog before connecting.
The USB Debug Adapter also provides a 5 V power source that can power the regulator. When powering the MCU
from the debug connector, the VBAT switch must be in the VREG position. Additionally, select the Power Target
after Disconnect check box in the Silicon Labs IDE connections options dialog to ensure the MCU always has
power.
5.5. Reset Button (SW6)
The reset push-button switch is in the lower-right corner. Pushing this button will always reset the MCU. Note that
pushing this button while the IDE is connected to the MCU will result in the IDE disconnecting from the target.