User's Guide _______________________________________________________________________
126 __________________________________________________________________ M211107EN-C
Operating LM21 through Maintenance Port
The following information is given for enabling operation of the LM21
through its maintenance terminal port in, for example, troubleshooting,
calibration, and operation checking situations.
In normal operation, LM21 parameters are set to the default values (see
Table 13 on page 102) and its communication line is released (closed) to
enable use by the host processor FSC202. This enables the operation of
the LM21 as part of an FS11P.
Serial Communication Settings
In this FS11P application, the default settings of the serial
communications port are as follows:
- 9600 baud
- No parity
- 8 data bits
- 1 stop bit
Serial Transmission RS-232
For the RS-232 communication, the Vaisala maintenance terminal cable
QMZ103 connects the LM21 signal wires to a standard PC/Laptop RS-
232 interface sub-D9 connector:
- RS-232 TxD to PC sub-D 3/9
- RS-232 RxD to PC sub-D 2/9
- GND to PC sub-D 5/9
Vaisala recommendation for the maximum length of the RS-232 cable is
50 m. Usually the RS-232 connection can be used with distances up to
100 m without problems, but this cannot be guaranteed.
Any computer equipped with terminal emulation software or a VT100
compatible terminal with RS-232 serial interface can be used as a
Maintenance Terminal for LM21.
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