ANNEX A - MODBUS OVERVIEW
54
A 1. INTRODUCTION
The FV300 can connect to a MODBUS network as a slave device conforming to V1.1 protocol
specification. The detector provides a bank of 16 bit registers to provide comprehensive
information on the status of the detector.
A status register is available so that a MODBUS controller can request the alarm and fault status
from the detector. Full location information is available for an alarm. The detector also supports
commands to perform OPM and alarm tests, reset latched alarms and faults and to control masking.
A 1.1 REFERENCES
MODBUS Application Protocol Specification V1.1, available from
MODBUS over serial line specification and implementation guide V1.0, available from
A 1.2 ELECTRICAL INTERFACE
The FV300 MODBUS interface operates on a 2-Wire serial bus in accordance with EIA/TIA-485
standard.
Note:
The Modbus serial bus must be fitted with a set of termination resistors at one
point only. See section 4.1.4.2 on page 12 of manual for details. When installing
on an existing bus check that the correct resistors have been fitted.
A 1.3 FV300 MODBUS SERIAL LINE PARAMETERS
The FV300 meets the Basic Implementation Class for a Slave device. These options are
summarised in Table. 5.
Basic
Default Value
FV300
Configurations
Node Addressing Configurable Address
from 1 to 247
1 to 247
Register Address
Offset
0 to 0xFFFF
Broadcast
Accept broadcast,
(target address 0)
Yes
(non configurable)
Baud Rate
9600 (19200
recommended)
19200
19200, 9600
Parity
EVEN
EVEN
EVEN, ODD, NONE
Mode
RTU
RTU
RTU only
Electrical
Interface
RS-485 2W-cabling
RS-485
2W-cabling
Connector Type
Screw Terminal
Table. 5
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