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7. Modbus tables
7.1. Modbus registers
Modbus Slave devices store data in registers. There are four register types and each type has its own register bank.
The register types are summarised below:
Register Name
Register Type
Description
Discrete Input
Digital Input
Read only register used for holding status information which holds
a value of 0 or 1.
Coil
Digital Output
Read and write accessible register which holds a value of 0 or 1.
Input Register
Analogue Input
Read only register used for status information which holds a 16-bit
value (0-65535)
Holding Register
Analogue Output
Read and write accessible register used for status information
which holds a 16-bit value (0-65535)
7.2. Discrete Inputs
This device has no Discrete Inputs.
7.3. Coils
Coils are read using function code 01 and written to using either function code 05 or 15. Function code 05 is used when
writing to a single coil register, function code 15 is used for writing to multiple coil registers in the same command.
Coils (Digital Outputs)
Register Name
Location
(decimal)
Length
Details
Drive On/Off
0
1
0x00 = Drive off
0x01 = Drive on
7.4. Input registers
Input Registers are read using function code 04.
Input Registers (Analogue Inputs)
Register Name
Location
(decimal)
Length
Details
Room Temperature in °C
0
1
Holds a temperature value in °C multiplied
by 10.
E.g. a value of 200 = 20°C
Fault Code
1
1
0x8000 = No error
0x6999 = Bad communication with indoor
unit
Summary of Contents for Procon A1M
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