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I have a Premium PLC with a processor TSX P572623.
I have configured the TER port as Character Mode link with 9600 baud, odd parity, 1 stop bit, and 7 data bits.

When I set the switch of the TSXPACC01 from master to slave, the PLC is immediately set in error mode (with TER, ERR and I/O LEDs on). The error persists even after reset as long as the switch is on the slave mode. To recover normal PLC status, I have to set the switch to master and reset again.
This phenomenon occurs even with empty applications (no code in MAST, Fast... tasks).

I have investigated the situation. The only setting that the PLC does not accept is the 7 data bits. If I use 8 data bits everything works fine.

As I am intending to connect the PLC to ABB SPA bus, I have to use 7 data bits.

Note:
The PLC OS version was 5.8, and I updated it to 6.1 without any change. The PL7Pro (4.4) library I have has only OS version TSX P572623 V5.6

So, is the communication with 7 data bits not supported by TER?

Thanks in advance.