STATUS SCIENTIFIC CONTROLS
Installation, Commissioning & Routine Gas Testing
FGD10A-M Gas Detector
TD18/032
Issue:
10
Change Note:
1869
Page 64
10.
MODBUS
INTERFACE
The FGD10A-M is supplied with an RS485 interface which provides control
of the FGD10A instrument via the Modbus RTU protocol. Remote calibration
and setup are possible as well as remote monitoring of the gas level and all
the other operational parameters of the FGD10A. Nearly all the front panel
menu (with the exception of the Modbus address) can be achieved remotely
via the Modbus protocol.
The Modbus node address must be set via the Menu option.
Note: For safety reasons the FGD10AM will NOT respond to Modbus
commands while in “Menu mode”. If the FDG10AM is left accidentally left in
menu mode it will time out after several minutes and Modbus
communications will be re-established.
Modbus (ISO/IEC 7498-1 Physical layer) description.
EIA RS485
9600 BAUD 8 data bits 1 start bit, 1
stop bit, no parity
2 WIRE
TWISTED PAIR UP TO 1.2 km in
length depending on number of
devices connected.
10.1. Modbus (ISO/IEC 7498-1 Application layer)
description.
Modbus RTU Frame Format
START
>=3.5 character width
ADDRESS
8 Bits
COMMAND
8 Bits
DATA
Multiples of 8 bits dependent on command
CRC
16 bits
END
>=3.5 character width
