User guide

SC932C 9-Pin to RS232-DCE Interface

B-2

B.2 Handshaking Lines

In its normal power mode, and when inactive (i.e. the datalogger ME line is low)

the SC932C only holds the RTS line high to provide a source of power to line-

powered modems, such as the RAD modem.

The DTR line is controlled by the ME line of the datalogger. When ME is high the

DTR line is powered high (>7V), but when the ME line returns to a low state, the

DTR line enters a high impedance state; as far as the RS232 device is concerned,

this has the same effect as the DTR line going low. This transition can be used to

force the device to go off-line, if the device supports this.

This feature is useful for some telephone modems as it allows the datalogger to

force the modem off-line. The older SC932 only supports this type of handshaking

when operated in its low power mode.

The SC932C can be modified to support a form of RTS

handshaking for the support of some specialised half-duplex

interfaces. Please contact Campbell Scientific for further details.

B.3 ‘Printer Only’ Output

The SC932C can be used as a printer (PE/SDE enabled) device. However, unlike

the SC932 where this mode can be set using internal jumpers, the SC932C requires

a special connection in place of the normal direct SC12 cable. The connection to

the SC932C should be made up as follows:

Figure B-1 Connections for Using SC932C in ‘Printer’ Mode

(Other wires can be left connected or disconnected.)

With this connection the SC932C can be connected in parallel to another

Campbell Scientific modem-type device. However, as with the SC932, any data

output to synchronous devices (e.g. a Storage Module) will also be transmitted out

through the RS232 connection.

B.4 Maximum Recall Interval

From the time that the datalogger leaves communications mode (ME goes low),

there is a delay of approximately one second before serial or ring line activity from

NOTE

Datalogger

Pin No.

SC932C

9-Way D

Pin No.

No connection to SC932C