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3.3.7 Connecting a 9 way socket to the SDM-SIO1A
+12V
G
C1
C2
C3
RG
G
RTS/TD+
TX/TD-
RX/RD+
CTS/RD-
3.4 Power conservation
To logger
Note 2
1) Note this diagram is for adding a 9 way d-type plug to the SDM-
SIO1A. A standard one to one serial lead
to connect to another piece of equipment (i.e. 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/RD- and RTS/TD+ 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.
The CTS/RD- and RTS/TD+ lines main use in RS232 mode are as
•
RTS/CTS hardware handshaking lines. CTS/RD- should be connected to
the remote equipment's RTS and RTS/TD+ to its CTS line.
•
The CTS/RD- (CTS) and RTS/TD+ (RTS) lines can also be used to
trigger external circuitry when not being used in handshaking mode.
Note: when using CTS/RD- and RT/TD+ lines as input and output that
the voltage levels are +/-5V NOT 0 and 5V.
CTS/RD- and RTS/TD+ can't be used as separate input and output when
•
in RS485 mode.
The SDM-SIO1A features an industry standard RS-232/RS-485 driver chipset
which ensures 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 wastage, the chip can be turned off when not in use, e.g.
between polled measurements, simply by closing the serial port, using Serialclose
User Guide
DTE configuration
RS232 9 way D-type connector
Pin 5
0V
Pin 7
RS232 RTS
Pin 3
RS232 TX
Pin 2
RS232 RX
RS232 CTS
Pin 8
* Note connection order
(Note 2)
can then be used
13
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