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Appendix B. Matching SDM-SIO1A
Connections to an SDM-SIO1
This section is provided for users who are familiar with the older SDM-SIO1,
so they can cross reference connections between the new and old devices.
The SDM-SIO1A has fewer terminals and different labeling than the
SDM-SIO1. It does, however, perform in exactly the same way and can be
used as a drop-in substitute with only minor changes to the wiring. It has fewer
terminals because the Z, Y, B, and A terminals are not present. For the
SDM-SIO1 these terminals were connected internally to the Tx, RTS, CTS
and Rx terminals respectively and were, therefore, duplicates. RS-422 and
RS-485 devices can be connected to the equivalent multifunction terminals on
the SDM-SIO1A.
The labeling for the RS-422/RS-485 functions has also been changed to avoid
the confusion caused by different labeling conventions used for the A and B
terminals by different manufacturers. To avoid this, the SDM-SIO1A uses the
alternative TD–, TD+, RD–, RD+ scheme of labeling, with the TD– and TD+
pair being those used for RS-485 half-duplex connections. Please refer to
TABLE
B-1
for a cross comparison between the connections for the
SDM-SIO1 and the SDM-SIO1A.
TABLE B-1. Pin Cross Connection Table for
SDM-SIO1 to SDM-SIO1A
SDM-SIO1
Case Text
C1
C2
C3
G
+12V
G
RX-A
CTS-B
RTS-Y
TX-Z
0V
Z
Y
B
A
SDM-SIO1A
Pin
Pin
1
3
2
4
3
5
4
2
5
1
6
7
7
10
8
11
9
8
10
9
11
6
12
9
13
8
14
11
15
10
Case Text
C1
C2
C3
G
+12V
G
Rx/RD+
CTS/RD–
RTS/TD+
Tx/TD–
RG
Tx/TD–
RTS/TD+
CTS/RD–
Rx/RD+
B-1
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