A Reference Guides; About Input Registers And Holding Registers; Modbus Data Model; Modbus Transactions - HMS Networks Anybus Communicator ABC3028 User Manual

Appendix A: Reference Guides
A Reference Guides
A.1

About Input Registers and Holding Registers

Modbus data is most often read and written as registers which are 16-bit pieces of data.
Holding registers and Input registers are both 16-bit registers.
Input registers
Input registers can only be read.
Holding registers
Holding registers can be read or written.
These registers can be used for a variety of things such as inputs, outputs, configuration data, or
other requirement for holding data.
A.2

Modbus Data Model

Discretes Input
Coils
Input Registers
Holding Registers
Reference: MODBUS Application Protocol Specification V1.1b3, April 26 2012
For more information refer to the Modbus organisation website.
A.3

Modbus Transactions

Nr
Transaction
1 Read Coils
2 Read Discrete
Inputs
3 Read Holding
Registers
4 Read Input
Registers
5 Write Single Coil
6
Write Single
Register
15
Write Multiple
Coils
16
Write Multiple
Registers
23
Read/Write
Multiple Registers
43/14 Read Device
Identification
Reference: MODBUS Application Protocol Specification V1.1b3, April 26 2012
For more information refer to the Modbus organisation website.
® ™
Anybus Communicator User Manual
Single bit Read-Only
Single bit Read-Write
16-bit word Read-Only
16-bit word Read-Write
Area
Function Code
Coils 0x01
Discrete 0x02
inputs
Holding 0x03
registers
Input registers 0x04
Coils 0x05
0x06
Holding
registers
0x0F
Coils
0x10
Holding
registers
0x17
Holding
registers
N/A 0x2B/0x0E
Data can be provided by the I/O system.
Data can be alterable by the application program.
Data can be provided by the I/O system
Data can be alterable by the application program.
Description
Read from 1 to 2000 contiguous status of coils in a
remote device.
Read from 1 to 2000 contiguous status of discrete
inputs in a remote device.
Read the contents of a contiguous block of holding
registers in a remote device.
Read from 1 to 125 contiguous input registers in a
remote device.
Write a single output to ON or OFF in a remote device.
Write a single holding register in a remote device.
In a sequence of coils, force each coil to either ON or
OFF in a remote device.
Write a block of contiguous registers in a remote
device.
Performs a combination of one read operation and
one write operation.
The write operation is performed before the read.
Read the vendor name, product code (article number),
firmware version, vendor URL and product name.
SCM-1202-162 1.1 en-US
121 (124)