3 setting the modbus master function, Setting the modbus master function -5 – Yokogawa Data Acquisition with PID Control CX2000 User Manual
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IM 04L31A01-17E
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Modbus Protocol
4.3
Setting the Modbus Master Function
Explanation
Selecting the Read Cycle
The cycle at which data is read from other devices. Select the read cycle from the
following:
125 ms, 250 ms, 500 ms, 1 s, 2 s, 5 s, 10 s, 15 s, 20 s, and 30 s
Selecting the Timeout Time
Timeout occurs if a response is not received from the specified slave device within the
time specified here (timeout time) after a command is sent from the CX. The CX
repeats the operation of sending a command and waiting for a response for the
number of times specified by the retrial (see below) value. If there is no response
from the slave device after the specified number of retrials, the CX stops sending
commands to the slave device.
Stop transmission
Operation when time out occurs (Example in which the retrial is set to 2)
: Command transmission from the CX (Transmitted at the read cycle)
: Response received from the specified slave device
: No response from the specified slave device
Recover during retrials
Time
Retry
Time
Retry
Yes
No
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
No
No
Select the timeout time from the following:
125 ms, 250 ms, 500 ms, 1 s, 5 s, 2 s, 10 s, and 1 min
Selecting the Number of Retrials
The number of times to retransmit the command when there is no response from the
specified slave device. If there is no response from the slave device after the
specified number of retrials, the CX stops sending commands to the slave device.
Select the number of retrials from the following:
Off (0 times), 1, 2, 3, 4, 5, 10, and 20
Setting the Commands
The commands are used to read the data in the register of slave devices as
communication input data of the CX at the selected read cycle. Data of consecutive
registers of the same data type in a slave device can be registered as a single group
and read as consecutive communication input data.
• Turning On/Off the commands
Turn [On] the command registration lines to be used. Up to eight commands can
be registered.