C8051F32x
Rev. 0.9 7
4.1. System Clock Sources
The C8051F320 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
applications an external oscillator is not required. However, if you wish to operate the C8051F320 device at a
frequency not available with the internal oscillator, an external crystal may be used. Refer to the C8051F32x data
sheet for more information on configuring the system clock source.
The target board is designed to facilitate the installation of an external crystal. Remove shorting blocks at headers
J9 and J10 and install the crystal at the pads marked Y1. Install a 10 M resistor at R9 and install capacitors at
C14 and C15 using values appropriate for the crystal you select. Refer to the C8051F32x data sheet for more
information on the use of external oscillators.
4.2. Switches and LEDs
Three switches are provided on the target board. Switch SW1 is connected to the RESET pin of the C8051F320.
Pressing SW1 puts the device into its hardware-reset state. Switch SW2 and SW3 are connected to the
C8051F320’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 blocks from the header to disconnect SW2 and SW3 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 is used to indicate a power
connection to the target board. The green LEDs labeled with port pin names are connected to the C8051F320’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.
Also included on the C8051F320 target board is a 10 K Thumb-Wheel Rotary Potentiometer, part number R14.
The Potentiometer is connected to the C8051F320’s GPIO pin through a header. Remove the shorting block from
the header to disconnect the Potentiometer from the port pin. The port pin signal is also routed to a pin on the J1 I/
O connector. See Table 1 for the port pin and header corresponding to the Potentiometer.
Table 1. Target Board I/O Descriptions
Description I/O Header
SW1 Reset none
SW2 P2.0 J3[1–2]
SW3 P2.1 J3[3–4]
Green LED P2.2 J3[5–6]
Green LED P2.3 J3[7–8]
Red LED PWR none
Potentiometer R14 J13
