Vaisala MMT330 - Manual (Page 81)

Chapter 4 _________________________________________________________________ Operation
VAISALA ________________________________________________________________________ 79
Serial Line Communication
Connect the serial interface by using either the user port or the service
port.
For permanent interfacing to host system, use the user port.You can
change the serial settings and operate in RUN, STOP, SEND, POLL, and
MODBUS modes.
For temporary connections use the service port. Service port is always
available with fixed serial settings.
0605-039
Figure 47 Service Port Connector and User Port Terminal
on Motherboard
The following numbers refer to Figure 47 above:
1 = Service port connector
2 = User port terminals