Chapter 4 ________________________________________________________________ Operation
VAISALA ______________________________________________________________________ 119
Operation of the RS-485 Module
RS-485 interface enables communication between RS-485 network and
DMT346 transmitter. The RS-485 interface is isolated and offers a
maximum communications rate of 115 200 bits/s. (For maximum bus
length of 1 km, use bit rate 19200 b/s or less.)
When selecting an RS-232-RS-485 converters for the network, avoid self
powered converters as they don't necessarily support the needed power
consumption.
Echo function shall be always disabled (OFF) when using the 2-wire
connection. When using the 4-wire connection you can disable/enable the
echo setting.
NOTE
User port on DMT346 main board cannot be used and connected when
RS-485 module is connected. Service port is operating normally.
Networking Commands
Set the RS-422/485 interface by using the following commands. The
other serial line commands are presented in section List of Serial
Commands on page 85.
RS-485 configuration commands
SERI
,
ECHO
,
SMODE
,
INTV
,
and
ADDR
may be issued by using either the service port or RS-422/485
port. Also the optional display/keypad can be used.
SERI
Use the
SERI
[
b p d s
] command to input RS-485 bus settings.
Syntax:
SERI
[
b p d s
]
where
b
=
baud rate (300, 600, 1200, 2400, 4800, 9600,19200, 38400,
57600, 115200)
p
=
parity (n = none, e = even, o = odd)
d
=
data bits (7 or 8)
s
=
stop bits (1 or 2)