Modbus Slave Protocol Specifications - YOKOGAWA Vigilantplant mR10000 User Manual

3.4

Modbus Slave Protocol Specifications

3-8
The Modbus slave protocol specifications of the recorder are as follows:
Serial Interface
Item
Transmission medium
Flow control
Baud rate
Start bit
Stop bit
Parity check
Transmission mode
Maximum number of
connected units
Slave Address
Address that can be set 1 to 32
Supported Functions
The function codes of the Modbus slave protocol that the recorder supports are shown
below. The recorder does not support broadcast commands.
Function Code
3
4
6
8
16
* Hexadecimal "00"
Communication Inpur Data
You can use the communication input data by describing it in the computing equations
for the computation channels.
Specifications
RS-422A/485
None only
Select from 1200, 2400, 4800, 9600, 19200, or 38400 [bps]
Fixed to 1 bit
Fixed to 1 bit
Select odd, even, or none (no parity).
RTU (Remote Terminal Unit) mode only
• Data length: 8 bits
• Data interval: 24 bits or less*
• Error detection: Uses CRC-16
* Determines message termination with a time interval to 3.5
characters or more.
Four-wire system: 32 slave devices
Two-wire system: 31 slave devices
Specifications
Read the hold register (4xxxx).
Read the input register (3xxxx).
Single write to hold register (4xxxx)
Loopback test
Write to the hold register (4xxxx)
Operation
The master device reads the
communication input data
written using function codes 6
and 16.
The master device loads the
computed, measured, alarm,
and time data of the recordr.
The master device writes to
the communication input data
of the recorder.
The master device performs a
loopback test of the recorder.
The recorder only supports
message return (test code
0x00*)
The master device writes to
the communication input data
of the recorder.
IM 04P01B01-17E