Rs232C Interface Specification - Multitech MMH900 User Manual

Appendix B

RS232C Interface Specification

The MultiMux RS232C interface circuits have been designed to meet the
electrical specifications given in the EIA (Electronic Industries
Association) RS232C and CCITT (Consultative Committee of
International Telegraph and Telephone) standards. All signals generated
by the mux are approximately 10 volts when measured across a load of
300 ohms or greater. The receiving circuits of the mux will accept signals
in the 3 to 25 volt range. The voltage thresholds are:
Negative =voltage more negative than -3 volts with respect to signal ground.
Positive =voltage more positive than +3 volts with respect to signal ground.
SIGNAL INFORMATION:
Binary State
Signal Condition
Control and Timing Function Off
The input impedances of all mux circuits which accept signals from the
data processing terminal or CPU equipment have DC resistances of
4.7K. For more specific details, consult the EIA RS232C standard itself.
The following chart lists the EIA RS232C interface pins and circuits
present on the mux RS232C interface connector. All other pins are
unused. The composite side of the mux is configured as a DTE device
and the channel sides are DCE devices.
PIN MULTI-TECH
ASSIGNMENT DESIGNATION
2 SD
3 RD
4 RTS
5 CTS
6 DSR
7 SG
B CD
9 +V
15 TC
17 RC
20 TR
22 Rl
24 XTC
25 OOS
*DTE
DCE
Appendix B - RS232C Interface Specifications
NEGATIVE
One
Mark
EIA CCITT SIGNAL
CIRCUIT CIRCUIT SOURCE* FUNCTION
BA 103 DTE
BB 104 DCE
CA 105 DTE
CB 106 DCE
CC 107 DCE
AB 102 ——
CF 109 DCE
+V -- DCE
DB 114 DCE
DD 115 DCE
CD 108/2 DTE
CE 125 DCE
DA 113 DTE
CN 142 DTE
= Data Terminal Equipment
=Data Communications Equipment
POSITIVE
Zero
Space
On
CIRCUIT
Transmitted Data
Received Data
Request to Send
Clear to Send
Data Set Ready
Signal Ground
Data Carrier detector
Test Voltage
Transmit Clock
Receive Clock
Data Terminal Ready
Ring Indicator
External Transmit
Terminal Busy
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