CI504-PNIO COM port with "Telegram Ending=Character Timeout" accessed by PNIO_COM_REC abnormal behavior

CPU PM591-ETH with CM579-PNIO and many remote i/o units in PROFINET with CI502-PNIO and CI504-PNIO. All "regular" tasks over the PROFINET are executed fine, but this one:

We need to communicate with several serial devices with diverse protocols over the serial ports of CI504-PNIO.

Ports are configured for ASCII-RS485.

The messages to be received are of variable length, so we need to set “Telegram Ending Selection” on “Character Timeout” (The only possible value for timeout with CI504 is 32 bits).

For programming we use “Automation Builder Standard v1.2”.

In the application program we use Function Blocks “PNIO_COM_SEND” and “PNIO_COM_REC” contained in the library “Profinet_Ext_AC500_V20.lib”.

It seems that PNIO_COM_REC returns data only if the receive buffer of the CI504-PNIO port is full, not when character timeout occurs (when the communication partner stops transmission).

We tested other “Telegram Ending” settings, like telegram length, and it appears that with these settings PNIO_COM_REC returns the received data as soon as the size is as instructed; but this is not appropriate for our case.

Is there any way to circumvent the problem?

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asked 3 months ago


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