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