Auxiliary Operations WebRelay Users Manual
Code Name Modbus
Function
Data Type* PLC Address
Mode 485
PLC Address
Mode 584/984
Coils (Read/Write) 01, 05 Discrete 1-1000 1-10000
Discrete Inputs (Read only) 02 Discrete 1001-2000 10001-20000
Registers (Read only) 04 8-64 bits 3001-4000 30001-40000
Holding Registers 16 8-64 bits 4001-5000 40001-50000
* Data types may be implemented at the discretion of the manufacturer. Address ranges may also over
lap. Discrete is a binary or boolean value, 1 or 0.
Function codes, memory types, and addresses can be converted to the PLC addressing equivalent
using the table below. To use the table, look up the row corresponding to the Modbus function code.
Then take the desired WebRelay feature address and add to it the address offset in the PLC address
mode column.
Code Name Modbus
Function
WebRelay Addresses Data Type PLC Address
Mode 485
PLC Address
Mode 584/984
Read Coils 01 0 (Relay 1) Discrete Addr + 1 Addr + 1
Read Discrete Inputs 02 0 (Input 1) Discrete Addr + 1001 Addr + 10001
Write Coils 05 0 (Relay 1) Discrete Addr + 1 Addr + 1
Write multiple
registers
16 784-791 ( Relay 1) 32-bit float Addr + 4001 Addr + 40001
5.3.3 WebRelay Full Address Table
The table below gives commonly used function codes, memory types, data sizes, and equivalent PLC
addresses for accessing the WebRelay. The data size will be the same regardless of the addressing
mode.
Function
Code
Address
(Decimal)
Data Size PLC Address
Mode 485
PLC Address
Mode 584/984
Read Relay Coil 01 0 Discrete 1 1
Write Relay Coil 05 0 Discrete 1 1
Read Discrete Input 02 0 Discrete 1001 10001
Pulse Relay 16 784 32-bit Float 4785 40785
Page 64 Xytronix Research & Design, Inc.
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