Execution Timing - Mitsubishi Electric MELSEC IQ-R series Reference Manual

Execution timing

The following shows the execution timing of send/receive processing while C24 is being sending/receiving other message of
MC protocol, when data transmission instruction by the on-demand function is executed in the CPU module.
When sending on-demand data or response data, the timeout check is performed by send monitoring timer
(timer 2). if a timeout error occurs, change the send monitoring time (timer 2).
When C24 is receiving request message of other command from external device
C24 sends on-demand data before the response message to the external device is sent.
• Full-duplex communication: C24 sends on-demand data during the request message from the external device is being
received.
Message of the other command
The C24 receives from
(Request message)
the external device.
The C24 transmits to
the external device.
CPU module
• Half-duplex communication: C24 sends on-demand data after the request message from the external device has been
received.
Message of the other command
The C24 receives from
(Request message)
the external device.
The C24 transmits to
the external device.
CPU module
When C24 is sending response message of other command to external device
C24 sends the on-demand data to the external device after the response message to the external device.
Message of the other command
The C24 receives from
(Request message)
the external device.
The C24 transmits to
the external device.
CPU module
13 SERIAL COMMUNICATION MODULE DEDICATED COMMANDS
282
13.6 On-demand function
On-demand data Message of the other command
(Response message) (Response message)
G(P).ONDEMAND G(P).ONDEMAND
On-demand data
(Response message)
G(P).ONDEMAND
Message of the other command
(Response message)
G(P).ONDEMAND
Message of the other command
(Response message)
On-demand data
(Response message)