21
Value control-
ling the first
analog output.
4015 0 0 0
Value control-
ling the second
analog output.
4016 1 1 1
Custom confi-
guration
4019 8 8 8
6. RS-485 INTERFACE
The P18(D) programmable digital transducers have a serial link
RS-485 for communication in the computer systems and with other de-
vices that serve as a Master. Asynchronous character MODBUS com-
munication protocol has been implemented in a serial link. The transmis-
sion protocol describes how to exchange information between devices
via a serial link.
Caution:
For the transmitter versions without analog outputs (P18 (D) -0XX
and P18 (D) -3XX), the RS-485 interface is galvanically isolated from
the supply - 1 kV separation.
For the transmitter versions with analog outputs, the RS-485 interfa-
ce is not isolated from the supply or from the analog outputs.
6.1. Connection of the serial interface
Standard RS-485 allows a direct connection up to 32 devices
on a single serial link to a length of 1200 m (at baud rate 9600 b/s).
It is necessary to use additional intermediate-separation circuits for con-
necting higher number of the devices, for example PD51 manufactured
by LUMEL S.A.
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