Manual

7-10
IM MV1000-17E
Modbus Master Function
Basic Operation
The MV, operating as a master device, communicates with slave devices periodically
by sending commands at specified intervals.
This function is independent of the Modbus client function operating over the Ethernet
interface.
The supported functions are (1) reading data from the input registers and hold
registers on a slave device and (2) writing data into the hold registers on a slave
device.
Serial Communication Specifications (same as with the Modbus slave
function)
Communication available via ModbusRTU
Communication media: RS-232, RS-422, or RS-485
Control system: No flow control (none only)
Baud rate: Select 1200, 2400, 4800, 9600, 19200, or 38400.
Start bit: 1 (fixed)
Data length: 8 (fixed)
Parity: Select odd, even, or none
Stop bit: 1 (fixed)
Message termination determination:
Time equivalent to 48 bits
Modbus Master Specifications
Read cycle: Select the cycle for reading data from other devices from the
following:
125 ms, 250 ms, 500 ms, 1 s, 2 s, 5 s, and 10 s
Timeout value:
Select the timeout value when there is no response from a
specified slave after sending a command from the MV.
125 ms, 250 ms, 500 ms, 1 s, 2 s, 5 s, 10 s, and 1 min
Retry count:
Select the retry count when there is no response from a
specified device for a command sent from the MV
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
W
ait between commands: Select the wait time
*
to send the next command after receiving
a response to the previous command from the following:
OFF, 5, 10, 15, 45, and 100 ms
* When communicating using an RS-485 two-wire system,
the signals may collide, because the master and slave
device communication drivers switch in half-duplex mode.
If communication does not work properly, increase the wait
time.
Command type:
R, R-M, W, and W
-M
Command setup: Set up to 16 commands
Command items: Read channel 201 to 440, C01 to C60
Write channel 001 to 048, 101 to 160 (varies depending on
the model)
Address:
1 to 247
Input registers: Same as the Modbus client function.
Hold register: Same as the Modbus client function.
Access method: Same as the Modbus client function.
Supported functions:
Same as the Modbus client function.
Data type: Same as the Modbus client function.
7.3 Modbus Protocol Specifications