Chapter 4 Modbus Protocol; Modbus Protocol Specifications And Function Codes - YOKOGAWA XL100 User Manual

Chapter 4 Modbus Protocol

4.1 Modbus Protocol Specifications and Function
Codes
Modbus Specifications
Function Codes of the Modbus Protocol
IM XL100C-E
The Modbus protocol can be used only on the serial interface (RS-232 or RS-485).
The Modbus specifications of the XL100 are as follows:
Specifications Description
Transmission media RS-232 or RS-485
Baud rate Select 2400, 4800, 9600, 19200, 38400, 57600, or 115200 bps (57600
and 115200 are selectable only on the RS-485)
Start bit Fixed to 1 bit
Stop bit Select 1 or 2 bits
Parity Select Odd, Even, or None (no parity).
Transmission mode RTU (Remote Terminal Unit) mode or ASCII mode
Data length RTU mode: 8 bits. ASCII mode: Select 7 or 8 bits
Error detection RTU mode: Uses error detection CRC-16. ASCII mode: Uses LRC
Data interval RTU mode: Determines message termination with a time interval
ASCII mode: Indicates message termination with CR+LF.
Slave address RS-232: 1 to 247
RS-485: 1 to 247
The function codes of Modbus protocol that the XL100 supports are listed below.
Slave Function
The slave function of the XL100 does not support broadcast commands.
Function Function
Code
3 Read the hold register (4xxxx)
4 Read the input register (3xxxx)
6 Single write to hold register (4xxxx) The master device writes to the communication
8 Loopback test
16 Write to the hold register (4xxxx)
* Hexadecimal 00.
Master Function
Function Function
Code
3 Read the hold register
(4xxxx and 4xxxxx)
4 Read the input register
(3xxxx and 3xxxxx)
equal to 3.5 characters or more.
Operation
The master device can read the communication
input data written using function codes 6 and 16.
The master device loads the calculated,
measured, and time data of the XL100.
input data of the XL100.
The master device performs a loopback test of
the XL100. The XL100 only supports message
return (test code 0x00*).
The master device writes to the communication
input data of the XL100.
Operation
Read the hold register data of another device into
communication input data (Cxx).
Read the input register data of another
device into communication input data (Cxx).
1
2
3
4
5
6
7
App
Index
4-1