SIGMA MRX Series User Manual
Page 20
APPENDIX A – SCI PROTOCOL AND INTERFACE
A10
RS-232C WIRING
SCI-MRX 9 PIN 'D'
SERIAL PORT
SERIAL PORT
PIN SIGNAL
CONNECTIONS
CONNECTIONS
DESIGNATION
(COMM 1-DCE)
(COMM 2-DTE)
1- N/C
N/C
N/C
2-
RECEIVE DATA (RXD) [INPUT]
RXD
OR
TXD
3-
TRANSMIT DATA (TXD) [OUTPUT]
TXD
OR
RXD
4-
DATA TERMINAL READY (DTR) [OUTPUT]
CTS
CTS
5- SIGNAL
GROUND
GROUND
GROUND
6-
DATA SET READY (DSR) [INPUT]
RTS
RTS
7-
READY TO SEND (RTS) [OUTPUT]
DSR
DSR
8-
CLEAR TO SEND (CTS) [INPUT]
DTR
DTR
9- N/C
N/C
N/C
Although the RS-232C standard defines the use of 25 pins, only nine of those are needed for basic PC
serial communications. Of those nine, only seven are required for serial communications with the SCI-MRX.
The above wiring chart is typical for most IBM and compatible type PC's. However, it is always best to check
with the manufacturer's wiring specifications to determine exact pin assignments before beginning. This is
especially true if using COMM 1, since some manufacturers use a 9 pin 'D' connector instead of a 25 pin 'D'.
Regardless of the connector, the signal connections are the same. RXD and TXD are reversed depending
upon whether the serial port is configured as a DTE (data terminal equipment) or a DCE (data communications
equipment).
If the control equipment does not require handshaking, there is no need to jumper the pins on the SCI-MRX. When handshaking
is not required only 3 pins will be used: TXD, RXD and Signal Ground. All other pins will have no connection.