User`s manual

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6.3 Transmission Monitoring Time (timer 2) Setting
The transmission monitoring time (timer 2) clears the wait state when the Q series C24 that is to transmit a message or
response message (result) has entered the transmission end wait state due to trouble in the external device.
When the Q series C24 transmits a message, it monitors the wait time up to the end of transmission of the message.
When the Q series C24 received a message from the external device, it monitors the wait time up to the end of
transmission of the response message.
The following explains the transmission monitoring time (timer 2) operation.
• If on-demand data is transmitted before a response message during data communications using an MC
protocol, each time is monitored.
(1) Q series C24 operation by transmission monitoring time (timer 2)
(a) When transmission monitoring time (timer 2) is set to 0ms
The time until transmission of the message or response message is not monitored. If the Q series C24 cannot
transmit, it waits infinitely.
(b) When transmission monitoring time (timer 2) is set to 100ms or longer
Monitors the time from completion of message or response message transmission preparations to the end of
transmission and returns the elapsed time to 0 at the end of transmission.
At time-out, the Q series C24 performs the following processing.
• Data communications using MC protocol
• While waiting for the end of transmission of the response message, the Q series C24 stores the error code
to the data transmission result storage area (buffer memory addresses 257H, 267H) for the target
interface. The Q series C24 enters the state in which it waits to receive the next command message
without sending a response message (NAK message) to the external device.
• During on-demand data transmission, the Q series C24 stores the error code to the on-demand execution
result storage area (buffer memory addresses 256H, 266H) for the target interface.
• If transmission was terminated midway in either of the cases above, the Q series C24 does not transmit
the remaining data.
Response message
Response message
Message
Message
Monitoring
time
Monitoring
time
External
device
Programmable
controller CPU
Elapsed time reset
On-demand data
Command message
Response message
Elapsed time reset
Monitoring
time
External
device
Programmable
controller CPU
Monitoring
time