Rabbit RabbitCore RCM5400W, User Manual, Page: 43 / 120

OEM User’s Manual 37
Table 3 summarizes the possible parallel port pins for the serial ports and their clocks.
4.2.1.1 Using the Serial Ports
The receive lines on the RCM5400W serial ports do not have pull-up resistors. If you are
using the serial ports without a receiver chip (for example, for RS-422, RS-232, or RS-485
serial communication), the absence of a pull-up resistor on the receive line will likely lead
to line breaks being generated since line breaks are normally generated whenever the
receive line is pulled low. If you are operating a serial port asynchronously, you can inhibit
character assembly during breaks by setting bit 1 in the corresponding Serial Port
Extended Register to 1. Should you need line breaks, you will have to either add a pull-up
resistor on your motherboard or use a receiver that incorporates the circuits to have the
output default to the nonbreak levels.
The Dynamic C
RS232.LIB
library requires you to define the macro
RS232_
NOCHARASSYINBRK
to inhibit break-character assembly for all the serial ports.
#define RS232_NOCHARASSYINBRK
This macro is already defined so that it is the default behavior for the sample programs in
the Dynamic C
SAMPLES\RCM5400W\SERIAL
folder.
Table 3. Rabbit 5000 Serial Port and Clock Pins
Serial Port A
TXA PC6, PC7, PD6
Serial Port E
TXE PD6, PE6, PC6
RXA PC7, PD7, PE7 RXE PD7, PE7, PC7
SCLKA PB1 RCLKE PD5, PE5, PC5
Serial Port B
TXB PC4, PC5, PD4 TCLKE PD4, PE4, PC4
RXB PC5, PD5, PE5
Serial Port F
TXF PD2, PE2, PC2
SCLKB PB0 RXF PD3, PE3, PC3
Serial Port C
TXC PC2, PC3 RCLKF PD1, PE1, PC1
RXC PC3, PD3, PE3 TCLKF PD0, PE0, PC0
SCLKC
PD2, PD7, PE2, PE7,
PC7
RCLKE and RCLKF must be selected to be on the
same parallel port as TXE and TXF respectively.
Serial Port D
TXD PC0, PC1
RXD PC1, PD1, PE1
SCLKD
PD0, PD3, PE0, PE3,
PC3