A Reference Guides; About Input Registers And Holding Registers; Modbus Data Model; Modbus Transactions - HMS Networks Anybus Communicator 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 0x03
4 Read Input Registers
5
Write Single Coil
6 Write Single Register
15
Write Multiple Coils
16
Write Multiple
Registers
22
Mask Write Register
23
Read/Write Multiple
Registers
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
Function Code Description
0x01 Read from 1 to 2000 contiguous status of coils in a remote device.
0x02
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.
0x04 Read from 1 to 125 contiguous input registers in a remote device.
0x05
Write a single output to ON or OFF in a remote device.
0x06 Write a single holding register in a remote device.
0x0F
In a sequence of coils, force each coil to either ON or OFF in a
remote device.
0x10
Write a block of contiguous registers in a remote device.
0x16
In a single transaction, modify the contents of a specified holding
register using a combination of an AND mask, an OR mask, and the
register's current contents.
Can be used to set or clear individual bits in the register.
0x17
Performs a combination of one read operation and one write
operation.
The write operation is performed before the read.
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.
SCM-1202-152 1.10 en-US
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