Rabbit RabbitCore RCM2200, User Manual

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User’s Manual 15
Two sample programs,
MASTER.C
and
SLAVE.C
, are available to illustrate RS-485 master/
slave communication. 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 RS-485 connections between the slave and master devices are as follows.
• RS485+ to RS485+
• RS485– to RS485–
• GND to GND
•
MASTER.C
—This program demonstrates a simple RS-485 transmission of lower case
letters to a slave RCM2200. The slave will send back converted upper case letters back
to the master RCM2200 and display them in the
STDIO window. Use
SLAVE.C
to pro-
gram the slave RCM2200—reset the slave before you run
MASTER.C
on the master.
•
SLAVE.C
—This program demonstrates a simple RS-485 transmission of lower case
letters to a master RCM2200. The slave will send back converted upper case letters
back to the master RCM2200 and display them in the
STDIO
window. Compile and run
this program on the slave before you use
MASTER.C
to program the master.
3.1.3 Other Sample Programs
Section 6.2 covers how to run the TCP/IP sample programs, which are then described in
detail.
The diagram shows the connections.
You will have to connect PC0 and
PC1 (Serial Port D) on the Prototyp-
ing Board to the RS-485 transceiver,
and you will connect PD3 to the RS-
485 transceiver to enable or disable
the RS-485 transmitter.
681 W
220 W
681 W
485+
485–
A
B
termi-
nation
bias
bias
Vcc
PC0
PC1
PD3
DI
RO
DE
/RE
Vcc
RS-485
CHIP
47 k W