18
RabbitCore RCM2100
Two sample programs,
MASTER2.C
and
SLAVE2.C
, are available to illus-
trate RS-485 master/slave communica-
tion. To run these sample programs,
you will need a second Rabbit-based
system with RS-485, and you will also
have to add an RS-485 transceiver
such as the SP483E and bias resistors
to the Prototyping Board.
The diagram shows the connections.
You will have to connect PC0 and PC1
(Serial Port D) on the Prototyping Board to the RS-485 transceiver, and you will connect
PD0 to the RS-485 transceiver to enable or disable the RS-485 transmitter.
The RS-485 connections between the slave and master devices are as follows.
•
RS485+ to RS485+
•
RS485– to RS485–
•
GND to GND
•
MASTER2.C
—This program demonstrates a simple RS-485 transmission of lower case
letters to a slave RCM2100. The slave will send back converted upper case letters back
to the master RCM2100 and display them in the
STDIO
window. Use
SLAVE2.C
to
program the slave RCM2100.
•
SLAVE2.C
—This program demonstrates a simple RS-485 transmission of lower case
letters to a master RCM2100. The slave will send back converted upper case letters
back to the master RCM2100 and display them in the
STDIO
window. Use
MASTER2.C
to program the master RCM2100.
3.1.3 Other Sample Programs
Section 6.7 covers how to run the TCP/IP sample programs, which are then described in
detail.
681
W
220
W
681
W
485+
485
A
B
termi-
nation
bias
bias
Vcc
PC0
PC1
PD0
DI
RO
DE
/RE
Vcc
RS-485
CHIP
47 k
W
