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13 SERIAL COMMUNICATION MODULE DEDICATED COMMANDS
13.6 On-demand function
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.
• Half-duplex communication: C24 sends on-demand data after the request message from the external device has been
received.
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
(Request message)
The C24 receives from
the external device.
On-demand data
(Response message)
Message of the other command
(Response message)
The C24 transmits to
the external device.
CPU module
G(P).ONDEMANDG(P).ONDEMAND
Message of the other command
(Request message)
The C24 receives from
the external device.
The C24 transmits to
the external device.
On-demand data
(Response message)
Message of the other command
(Response message)
CPU module
G(P).ONDEMAND
Message of the other command
(Request message)
The C24 receives from
the external device.
Message of the other command
(Response message)
On-demand data
(Response message)
The C24 transmits to
the external device.
CPU module
G(P).ONDEMAND
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