
App-2
M-4662
Appendix 2 Data Dropout during Modbus
Communication
DataDropoutWhenOperatingasaModbusClient
If the MV tries to issue a command to a server 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
(Servers 2 and 3)
Data dropout
(Server 3)
Server device 1
Server device 2
Server device 3
G
G
G
G
G
G
Read cycle
(Retry)
: Status lamp
: Response from the server device
: Command from the MV
Data dropout
(Servers 2 and 3)
Server device 1
Server device 2
Server device 3
Read cycle
Timeout value
Connection dropped
Data dropout
(Servers 2 and 3)
Server device 1
Server device 2
Server device 3
G
G
G
G
G
G
G
O
Connection dropped Connection recovered
Timeout value
G
G
G
G
O
Y
Connection retry time*
G G
G G G
G
Y
O R
1. When the response from the server device takes a long time
2. When the connection is dropped because there is no response from the server device
3. When the communication recovers through connection retry
* The first connection retry after the connection is
dropped is shorter than the specified interval. The
status lamp indications in this example apply
when the connection retry function is enabled.
Comentarios a estos manuales