Question:
Why can some function blocks not be used in the system POE 'PLC_ColdStart'?
Answer:
'PLC_ColdStart' is a hardware-dependent system POE which is made available by the PLC. It is only called once per request and can comprise a maximum of 1,000 statements. It is triggered automatically by the system after a RESET or program download with the START command. When this POE has been executed the CAN/AIF bus is ready.
Function blocks which have to be called a number of times in order to process a function must not be used in the PLC_ColdStart because the latter is only processed exactly once so the function of the function block is not executed completely. Examples of function blocks which must not be called in PLC_ColdStart are L_ParRead and L_ParWrite.
