User`s manual

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3.3.7 Precautions when using the modem function
Precautions when using the modem function to perform data communication with an external device via public line or
call to the pager receiver are described.
(1) Line connection and disconnection
When performing data communication with an external device, it must be predetermined which station is to
perform the line connection (dialing) and disconnection processing with the partner device as well as the timings.
(2) Reception data before connection completion
Before the connection processing to the modem is completed the reception data other than modem commands is
ignored (read and disposed) at the interface that uses the modem function.
The Q series C24 will ignore the data even when an MC protocol command message is received.
(3) Transmission control
Delays may occur in transmission controls to notify the data reception capability at the local station to the partner
device.
In order not to have a state in which the partner device cannot receive the transmission data, the amount of
transmission/reception data and intervals should be determined beforehand.
When transmission/reception data in the non procedure protocol, the procedure must also be predetermined.
(4) Priority of data communication and notification
After line connection is established, the data transmission/reception processing with the partner device is
performed in the order of the processing request occurrence.
At the same time, when the line disconnect processing or data transmission reception (including data
transmission processing, reception processing and Flash ROM access processing) occurs, the line disconnect
processing has the priority.
(5) Data communication time
The data transmission/reception time after line connection has been established with the partner device is the
total time of the transmission time between the Q series C24 and modem/TA, between modem and TA, and
between modem/TA and partner device.
When communicating via the MC protocol, the transmission time (such as T0 and T3) indicated in the MELSEC
Communication Protocol Reference Manual must include the transmission time between the Q series C24-side
modem/TA and the destination device.