Yokogawa Button Operated MV2000 - Manual (Page 167)

App-3 M-4662
Appendix
1
2
3
4
5
6
7
App
Index
Data Dropout While Operating as a Modbus Master
If the MV tries to issue a command to a slave device but has not finished receiving
a response to the previous command, the MV will not be able to transmit the next
command. This will cause a data dropout. Take appropriate measures to prevent
dropouts 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 MV
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 set to 1)
G
G
G
G
G
G G
G
G
G
G G
G
Y R
Appendix 2 Data Dropout during Modbus Communication