The Modem Stops Polling After First Poll; Polling Occurs, But Will Not Dial On Demand; Modem Occasionally Hangs-Up During Wat Data Exchange; Occasional "Re-Tries" Occur During Programming/Monitoring - Mitsubishi Electric A2S-MODEM User Handbook Manual

4.4 The Modem Stops Polling After First Poll

1. Only applies to Dial On Demand polling
2. Check that the serial cable that you are using to connect to the PLC is right for the
PLC.
3. If using a communications module, check that its settings are correct
4. If connected to an HMI terminal, check that its communications settings are
correct

4.5 Polling Occurs, but will not Dial On Demand

1. Check that the register address polled is correct, AT%ADR setting.
2. Check that the PLC program is setting the RQ bit.
3. Check that there is at least one value in the telephone register of the command
block, and that it the value has sufficient trailing 0's, i.e. 1000 not 1.
4. If using speed-dial numbers, check that the number requested is set in the modem,
At&Zn setting.

4.6 Modem occasionally hangs-up during WAT data exchange.

This is usually caused by an unacceptable number of data errors, detected during a
WAT operation.
1. Check cable connections.
2. The problem may be caused by poor Telephone Network connections, for
example, Exchange faults or old lines.
3. Try reducing the Baud rate between the A2s Modems on the Network by
changing the AT%NET setting from the default 28800 rate.

4.7 Occasional "Re-tries" occur during Programming/Monitoring.

This is probably due to poor Telephone Network connections.
1. Try another Line or redial.
2. If you are dialling from a Mitsubishi A2S/DESK Modem try reducing the Baud
rate, using the AT%NET command.
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