C8051F36x-DK
6
Rev. 0.1
6.1. System Clock Sources
The C8051F360 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
3.0625 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 C8051F360 device at a
frequency not available with the internal oscillator, an external crystal may be used. Refer to the C8051F36x 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
J10 and J11 and install the crystal at the pads marked Y1. Install a 10 M
Ω
resistor at R1 and install capacitors at
C20 and C19 using values appropriate for the crystal you select. Refer to the C8051F36x data sheet for more
information on the use of external oscillators.
6.2. Switches and LEDs
Three switches are provided on the target board. Switch RESET is connected to the RESET pin of the C8051F360.
Pressing RESET puts the device into its hardware-reset state. Switches P3.0 and P3.1 are connected to the
C8051F360’s general purpose I/O (GPIO) pins through headers. Pressing P3.0 or P3.1 generates a logic low
signal on the port pin. Remove the shorting blocks from the J12 header to disconnect Switch P3.0 and Switch P3.1
from the port pins. See Table 1 for the port pins and headers corresponding to each switch.
Four 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 surface-mount LEDs labeled with port pin names are connected to the
C8051F360’s GPIO pins through headers. Remove the shorting blocks from the header to disconnect the LEDs
from the port pin. The USB ACTIVE red LED indicates when the CP210x USB-to-UART bridge (U3) on the board is
receiving power from the USB bus and is properly enumerated (i.e. drivers are installed and a USB cable is
connected to P4). See Table 1 for the port pins and headers corresponding to each LED.
Also included on the C8051F360 target board is a 10 K
Ω
thumb-wheel rotary potentiometer, part number R10. The
potentiometer is connected to the C8051F360’s P2.5 pin through the J13 header. Remove the shorting block from
the header to disconnect the potentiometer from the port pin. 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
P3.0
J12[1–2]
SW3
P3.1
J12[3–4]
Green LED
P3.2
J12[5–6]
Green LED
P3.3
J12[7–8]
Red LED
PWR
none
Red LED
USB ACTIVE
none
Potentiometer
P2.5
J13
