Appendix A - Mk1 Data Base
Publication PUB091-003-00_0119
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12.3 Modbus Communication
The electrical properties of the MFU in Mk1 mode are the same as in Mk2 mode:
Line Electrical Specification:
RS-485, two-wire, half duplex (4 wire not supported)
Modbus Transmission Mode
RTU (8 bit Binary data)
Supported Baud Rates
300, 600, 1k2, 2k4, 4k8, 9k6, 19k2, 38k4, 57k6, 115k2
(2k4, 4k8, 9k6, 19k2, 38k4, 57k6, 115k2 when using the
internal repeater option)
Number of bits per character
1 start bit, 8 data bits, Parity bit, 1 or 2 stop bits
Parity (configurable)
Odd, Even, None
Variants
Single highway plus analogue input
Dual highway (one common address and baud rate)
Single highway with repeater
12.4 Modbus Data Base
Message format:
RTU
Modbus Address:
1 to 247 (Dual channel version both channels must have
the same address.)
12.4.1 Function Code Support
Function
Code
Modbus Name
Addressing
01
Read Output Coil Status
Discrete
02
Read Input Status
Discrete
03
Read Holding Registers
Register
04
Read Input Registers
Register
05
Force Single Coil
Discrete
06
Preset Single Register
Register
07
Read Exception Status
08
Loopback Diagnostic Test
15
Force Multiple Coils
Discrete
16
Preset Multiple Registers
Register
17
Report Slave ID
12.4.2 Broadcast Messages
Broadcast messages using code 05 and 06 are allowed to the following functions
Open command
ESD command