Yokogawa Value Series FX1000 - Manual (Page 192)

App-2
IM 04L21B01-17EN
Data Dropout during Modbus Master
If the response to the previous command is not complete when the FX attempts to issue
a command to a slave device, the FX cannot issue the command causing a data dropout.
Take appropriate measures by referring to the following figures.
Read cycle
Data dropout
(slaves 2 and 3)
Data dropout
(slave 3)
Slave device 1
Slave device 2
Slave device 3
G
G
G
Read cycle
(Retry)
: Status lamp
: Response from the slave device
: Command from the FX
Data dropout
(slaves 2 and 3)
Data dropout
(slaves 2 and 3)
Disconnect slave 2
Slave device 1
Slave device 2
Slave device 3
Read cycle
Timeout value
Data dropout
(slaves 2 and 3)
Slave device 1
Slave device 2
Slave device 3
G G
G
G
Y
Timeout value
G Y
Timeout value
R
1. When the response from the slave device takes a long time
2. When there is no response from the slave device
3. When the slave device that is not responding is disconnected (retry count is set to 1)
G
G
G
G
G
G G
G
G
G
G G
G
Y R
Appendix 1 Data Dropout during Modbus Communication