CWT GFM A0A0161 - 12.0 Modbus Specifications; 12.1 GFM Modbus Register Data; 12.2 Modbus Coils CR [1..16]

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12.0 MODBUS SCPECIFICATIONS
12.1 GFM MODBUS REGISTER DATA
This document provides the basic Modbus memory map and command structure for the GFM
RS-485 communications port. The GFM supports the Modbus Protocol as specified in the
Modicon Technical publications “Modbus Protocol” (intr7.html). The GFM control does not support
the Broadcast mode. The controller provides the slave side communications routines for the RTU
mode. The user must set the Slave ID to 1-247 the default ID is set to 1. Default Baud rate is
19.2 K baud with 8 data bits, One Stop and no parity. The following Modbus commands are
supported:
CODE
DESCRIPTION
ADDRESS RANGE
01
Read Coil Status
1-49
03
Read Holding Registers
1-124
05
Force Single Coil
1-49
06
Preset Single Register
1-124
15
Force Multiple Coils
1-49
16
Preset Multiple Registers
1-124
17
Report Slave ID
5 bytes
All Modbus Register values are word sized unsigned integer unless otherwise indicate.
12.2 MODBUS COILS CR [1..16]
INPMSK - Simulated Relay Inputs CR [1...8]
• Bit 0 = Enable Log Mode
• Bit 1 = Enable Metric
• Bit 2 = Enable Alarms
• Bit 3 = Reset Volume
• Bit 4 = Reset RTC
• Bit 5 = Spare 1 – Not used
• Bit 6 = Spare 2 – Not used
• Bit 7 = Spare 3 – Not Used
RELMSK - Simulated Outputs CR [9...16]
• Bit 0 = System Ready Output
• Bit 1 = Gas Flow Active
• Bit 2 = Gas Flow Low Limit
• Bit 3 = Gas Flow Ok – Hardware SSR Relay Output
• Bit 4 = Gas Flow High Limit
• Bit 5 = Low Gas Volume level alarm
• Bit 6 = Spare 4 – Not used
• Bit 7 = Spare 5 – Not used