Campbell Scientific SDM-SIO1 Serial Input/Output Module - Manual (Page 19)

SDM-SIO1 Serial Input/Output Module
3.3.7 Connecting a 9-Way Socket to the SDM-SIO1
1 C1
2 C2
3 C3 To logger
4 G DTE Configuration
5 +12V RS-232 9-Way Dtype Connector
6 G 0V Pin 5
7 RX-A RS-232_TX Pin 3
8 CTS-B RS-232 CTS Pin 8
9 RTS-Y RS-232 RTS Pin 7
10 TX-Z RS-232 RX Pin 2
11 0V
Note 2
12 Z
13 Y
14 B
15 A
1) Note this diagram is for adding a 9 way D-type plug to the SDM - SIO1. A
standard one to one serial lead can then be used to connect to another piece of
equipment (e.g. a PC or sensor)
2) Since there is no standard that indicates whether certain devices should be
DTE or DCE it may be necessary to reverse the CTS – B and RTS-Y pins
when wiring hardware handshaking. You may cross the wires either by
crossing them manually (as shown by dotted lines) or, by purchasing a special
cable for this purpose.
Notes:
• The CTS-B (CTS) and RTS-Y (RTS) lines can also be used to trigger external
circuitry if desired when not being used in handshaking mode. Note that when
using CTS-B and RTS-Y lines as input and output that the voltage levels are
+/-12V NOT 0 and 5V.
• CTS-B and RTS-Y can’t be used as separate input and outputs when in RS-
485 mode.
3.4 Power Conservation
The SDM-SIO1 features an industry standard RS-232/RS-485 driver chipset
(Maxim 3160) which insures maximum likelihood of compatibility with all
other devices. When the driver is powered on it uses more power than one of
the datalogger’s control port based “com ports” – typically 6 mA minimum,
partly because it generates the correct signal levels which in itself requires
power and partly because, in the case of RS-232 signals, the resting state of
~–6V driving a nominal RS-232 ~3k load implicitly wastes ~2 mA of current
per line.
To avoid excess current use, the chip can be turned off when not in use, e.g.
between polled measurements, simply by closing the serial port, using
Serialclose (see below). When running in RS-232 mode with a sensor that only
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