C8051F326/7-DK
6
Rev. 0.2
6.1. System Clock Sources
The C8051F326 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 1.5 MHz
(±1.5%) by default but may be configured by software to operate at other frequencies. Therefore, in many applica-
tions an external oscillator is not required. However, if you wish to operate the C8051F326 device at a frequency not
available with the internal oscillator, an external CMOS oscillator may be used. Refer to the C8051F326/7 datasheet
for more information on configuring the system clock source.
The target board is designed to facilitate the installation of an external CMOS oscillator. Remove shorting block at
header J10 and connect the oscillator output to the header. Refer to the C8051F326/7 datasheet for more informa-
tion on the use of external oscillators.
6.2. Switches and LEDs
Three switches are provided on the target board. Switch S1 is connected to the /RST pin of the C8051F326. Press-
ing S1 puts the device into its hardware-reset state. Switches S2 and S3 are connected to the C8051F326’s gen-
eral purpose I/O (GPIO) pins through headers. Pressing S2 or S3 generates a logic low signal on the port pin.
Remove the shorting blocks from the header to disconnect S2 and S3 from the port pins. The port pin signals are
also routed to pins on the J1 I/O connector. See Table 1 for the port pins and headers corresponding to each
switch.
Three LEDs are also provided on the target board. The red LED labeled PWR LED is used to indicate a power con-
nection to the target board. The green surface mount LEDs labeled with port pin names are connected to the
C8051F326’s GPIO pins through headers. Remove the shorting blocks from the header to disconnect the LEDs
from the port pin. The port pin signals are also routed to pins on the J1 I/O connector. See Table 1 for the port pins
and headers corresponding to each LED.
6.3. Universal Serial Bus (USB) Interface (J9)
A Universal Serial Bus (USB) connector (J9) is provided to facilitate connections to the USB interface on the
C8051F326. Table 2 shows the J9 pin definitions.
Table 1. Target Board I/O Descriptions
Description
I/O
Header
S1
Reset
none
S2
P2.0
J3[1–2]
S3
P2.1
J3[3–4]
Green LED (D4)
P2.2
J3[5–6]
Green LED (D2)
P2.3
J3[7–8]
Red LED
PWR
none
Table 2. J9 USB Connector Pin Descriptions
Pin #
Description
1
VBUS
2
D–
3
D+
4
GND (Ground)
