Campbell Scientific CSM1 Card Storage Module - Manual (Page 19)

CSM1 Card Storage Module
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It is critical that line 4 does not go positive before line 20. This
can either be done under careful software control, or by tying the
two lines together at the SC532(A) and using just one line on the
computer to pull the two lines high on the SC532(A).
If it is not possible to control these lines by software, then the
older SM232A is available that uses a mechanical switch to
emulate setting the lines high or low. Please contact Campbell
Scientific for further details.
7.2 Establishing Communications
After raising the lines as described above, a series of carriage return characters
(ASCII decimal 13) with a 100ms delay between them must be sent to the
CSM1 to enable it to determine the baud rate for communication.
The CSM1 works with a serial format of eight bits, one start bit, one stop bit,
and no parity. Valid baud rates are 300, 600, 1200, 2400, 4800, 9600, 19200,
and 38400. Please contact Campbell Scientific for further advice before
attempting to use speeds of 38400.
Normally, the CSM1 will respond to the second carriage return sent to it with
the standard telecommunication prompt, a '?' preceded by carriage return,
linefeed.
7.3 Breaking Communications
Communications are broken either by taking lines 4 and 20 low, or by
removing power from the CSM1, e.g. unplugging the SC532(A) power supply.
NOTE