Yokogawa Value Series FX1000 - Manual (Page 188)

6-14
IM 04L21B01-17EN
Modbus Master Function
Basic Operations
• The FX, as a Modbus master device, communicates with Modbus slaves periodically
by sending commands at specified intervals.
• The Modbus master function operates independently from the Modbus client function
via the Ethernet communication.
• The supported functions are “reading data from the input registers and hold registers
on the slave” and “writing data into the hold registers on the slave.”
Serial Communication Specifications (Common to the Modbus Slave
Function)
Communicate via ModbusRTU
Communication media: RS-232, RS-422A/485
Control system:
No flow control (“None” only)
Baud rate: Select from 1200, 2400, 4800, 9600, 19200, and 38400
Start bit: 1 bit (fixed)
Data length: 8 bit (fixed)
Parity: Select odd, even, or none
Stop bit: 1 bit (fixed)
Message termination determination:
Time equivalent to 48 bits
Modbus Master Specifications
Read cycle: Select the cycle at which data is read from other devices from
the following:
1, 2, 5, and 10 s
Timeout value: Select the timeout value when there is no response from the
specified slave after sending a command from the FX from the
following:
125, 250, 500ms, 1, 2, 5, 10 s, and 1 min
Retry count: Select the retry count when there is no response for a
command sent from the FX to the specified slave.
OFF, 1, 2, 3, 4, 5, 10, and 20
Auto recovery cycle: Select the cycle for automatically recovering from the following:
OFF, 1, 2, 5, 10, 20, 30 min, and 1 h
Wait between commands: Select the wait time 1 after receiving a response of a command
until sending the next command from the following:
OFF, 5, 10, 15, 45, and 100 ms
1: When communicating using an RS-485 two-wire system, the
signals may collide, because the master and slave devices
driving the communication switch in half-duplex mode. If the
communication does not work, increase the wait time.
Command type: R-M, W, W-M
Command setting: Set up to 16 commands
Command items: Read channels C01 to C24
Write channels 001 to 012 and 101 to 124 (depends on the
model)
Address: 1 to 247
Input register: 30001 to 39999, 300001 to 365535
Hold register: 40001 to 49999, 400001 to 465535
Access method: Same as the Modbus client.
Supported functions: Same as the Modbus client.
Data type: Same as the Modbus client.
6.3 Modbus Protocol Specifications