Why do I sporadically get communication errors when connecting a PCD/PCS in "Secure S-Bus Data Mode"?

FAQ #101180

In case a "non Saia PCD® COSinus" PCD or PCS1 system is connected with "Secure S-Bus Data mode" (e.g. over a serial cable or over modem) from time to time a telegram is not answered correctly.


A PCD or a PCS connected with another system (e.g. PC or another PCD system) using the "Secure S-Bus Data mode" does not answer a telegram from time to time. This can e.g. be seen by a red LED on transmit or receive FBoxes (or in case a PC is used, by interpreting the tracewin files).
This phenomenon can be observed on PCD1.M1x5, PCD2.M150, PCD2/4.M170 and PCS1 systems (with firmware which are supporting the "Secure S-Bus Data mode"). Saia PCD® COSinus based systems (PCD2.M480, PCD2.M5xx0 and PCD3) are not concerned.

The reason for this behavior is that the PCD/PCS does not correcly answer telegrams where the sequence number in the secure S-Bus Data Mode header is 0xC5h. This is the case in every 255th telegram.
(The character "C5" should be replaced by "C5 01" but this is not done).

Please refer to the table below for firmware version which do correctly handle the "C5" and therefore the symptom described above is avoided.

 System Firmware 



PCD1 / _Firmware Classic

PCD2 / _Firmware Classic

PCD4 / _Firmware

PG5 2.0 / Serial-S-Bus

Last update: 29.05.2015 00:32

First release: 03.04.2009 11:35

Views: 32981

The requested software / document is no longer marketed by Saia-Burgess Controls AG and without technical support. It is an older software version which can be operated only on certain now no longer commercially available products.