A N 1 7 2
6
Rev. 0.4
6.1. System Clock Sources
The C8051F020 device installed on the target board features a calibrated programmable internal oscillator which is
enabled as the system clock source on reset. After reset, the internal oscillator operates at a frequency of 2 MHz
(±2%) by default but may be configured by software to operate at other frequencies. Therefore, in many applications
an external oscillator is not required. However, an external 22.1184 MHz crystal is installed on the target board for
additional applications. Refer to the C8051F02x data sheet for more information on configuring the system clock
source.
6.2. Switches and LEDs
Two switches are provided on the target board. Switch SW1 is connected to the RESET pin of the C8051F020.
Pressing SW1 puts the device into its hardware-reset state. Switch SW2 is connected to the C8051F020’s general
purpose I/O (GPIO) pin through jumpers. Pressing SW2 generates a logic low signal on the port pin. Remove the
shorting block from the jumper to disconnect SW2 from the port pins. The port pin signal is also routed to a pin on
the J24 I/O connector. See Table 1 for the port pins and jumpers corresponding to each switch.
Two LEDs are also provided on the target board. The red LED labeled PWR is used to indicate a power connection
to the target board. The green LED labeled with a port pin name is connected to the C8051F020’s GPIO pin
through jumpers. Remove the shorting block from the jumper to disconnect the LED from the port pin. The port pin
signal is also routed to a pin on the J24 I/O connector. See Table 1 for the port pins and jumpers corresponding to
each LED.
6.3. Target Board JTAG Interface (J4)
The JTAG connector (J4) provides access to the JTAG pins of the C8051F020. It is used to connect the Serial
Adapter to the target board for in-circuit debugging and Flash programming. Table 2 shows the JTAG pin defini-
tions.
Description
I/O
Jumper
SW1
Reset
none
SW2
P3.7
J1
Green LED
P1.6
J3
Red LED
PWR
none
Table 1. Target Board I/O Descriptions
Pin #
Description
1
+3 VD (+3.3 VDC)
2, 3, 9
GND (Ground)
4
TCK
5
TMS
6
TDO
7
TDI
8, 10
Not Connected
Table 2. JTAG Connector Pin Descriptions
