C 8 0 5 1 F 2 x x - D K
6
Rev. 0.6
6.1. System Clock Sources
The C8051F2xx device installed on the target board features a internal oscillator which is enabled as the system
clock source on reset. After reset, the internal oscillator operates at a frequency of 2MHz (+/-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 crystal may be installed on the target board for additional
applications. The target board is designed to facilitate the installation of an external crystal at the pads marked Q1.
Refer to the C8051F2xx datasheet for more information on configuring the system clock source. Following are a
few part numbers of suitable crystals:
Freq(MHz)
Digikey P/N
ECS P/N
22.1184
X063-ND
ECS-221-20-1
(20 pF loading capacitance)
18.432
X146-ND
ECS-184-20-1
(20 pF loading capacitance)
11.0592
X089-ND
ECS-110.5-20-1
(20 pF loading capacitance)
6.2. Switches and LEDs
Two switches are provided on the target board. Switch SW1 is connected to the RESET pin of the C8051F2xx
device on the target board. Pressing SW1 puts the device into its hardware-reset state. The device will leave the
reset state after SW1 is released. Switch SW2 is connected to the device’s general purpose I/O (GPIO) pin through
headers. Pressing SW2 generates a logic low signal on the port pin. Remove the shorting block from the header to
disconnect SW2 from the port pins. The port pin signal is also routed to a pin on the J2 I/O connector. See Table 1
for the port pins and headers 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 device’s GPIO pin through
headers. Remove the shorting block from the header to disconnect the LED from the port pin. The port pin signal is
also routed to a pin on the J2 I/O connector. See Table 1 for the port pins and headers corresponding to each LED.
6.3. Target Board JTAG Interface (J4)
The JTAG connector (J4) provides access to the JTAG pins of the C8051F2xx. 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 2
shows the JTAG pin definitions.
Table 1. Target Board I/O Descriptions
Description
I/O
Header
SW1
Reset
none
SW2
P2.5
P2.5
Green LED
P2.4
LED
Red LED
PWR
none
Table 2. JTAG Connector Pin Descriptions
Pin #
Description
1
+3VD (+3.3VDC)
2, 3, 9
GND (Ground)
4
TCK
5
TMS
6
TDO
7
TDI
8, 10
Not Connected
