Cisco IR829 Hardware Installation Manual page 37

Product Overview
RS232
1 DCE Ready, used as DSR in IOS
2 Received Line Signal Detector
3 DTE Ready
4 Signal Ground
5 Received Data
6 Transmitted Data
7 Clear To Send
8 Request To Send
Cisco refers to the signal on pin 1 as DSR. Use the show interface async 0 (or 1) from the IOS command
line will give you the state of the modem control signals on the last line:
DCD=up
Note: The Serial 0 and Serial 1 pin out is different from the Console/Auxiliary port, do NOT use the RJ-45
to DB-9 Blue colored Console Cable (72-3383-01).
DTE to DCE
While the equipment shown in
the concept of DTE (Data Terminal Equipment) and DCE (Data Communication Equipment) comes from the
use of dial-up modems that were used on the telephone network until the late 1990's.
Figure 11: Traditional DTE to DCE concept
Table 7: RS-232 logic and voltage levels
Data Circuits
0 (space)
1 (mark)
DSR/RI output
DCD output
DTR input
COM
RxD output
TxD input
CTS output
RTS input
DSR=up DTR=down RTS=down
Figure 11: Traditional DTE to DCE concept, on page 35
Control Circuits
Asserted
Deasserted
Cisco IR829 Industrial Integrated Services Router Hardware Installation Guide
RS485 Full Duplex
input TX+
input TX-
output RX-
COM
input
output RX+
input
output
CTS=up
Voltage
+3 to +15 V
-15 to -3 V
DTE to DCE
RS485 Half Duplex
output T X / R X + <->
output T X / R X - <->
input
COM
input
is less common today,
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