Introduction.

Workshop PG5
Instructionlist
Now the programming
begins:
Input
Input Input Output
Input
The ACCU is always set to high at the start of a block, therefore we don't have
to set the ACCU first.
A combination always starts with STH , STL, ACC L or
ACC H:
sth
Cond_Run
orh NormalRun
out IntermediateFlag
sth IntermediateFlag
anl Emergency
anh OilHigh
out OilPump
Set the ACCU to the state of the NormalRun signal ( =
IF NormalRun )
If the ACCU was set by Cond_Run OR NormalRun
Save the result in an intermediate flag and start a new
combination:
If the result of the Or function was high
AND The Emergency signal is Low
AND the OilHigh signal is active
Then the ACCU is set and we just copy the ACCU state
to the signal OilPump
Why did we solve the OR combination ( the parallel contacts NormalRun
Cond_Run ) first, before we tested the AND combinations ( Serial contacts
Emergency, OilHigh, and (NormalRun or Cond_Run))?
One important thing you have to remember is that an OR function
has absolute priority over the AND ( ANd High or ANd Low )
function.
If an OR function sets the ACCU, then the results of the following AND & OR
functions don't matter anymore until you start a new combination with STH. or
ACC H/L.
PG5-07-E © Saia-Burgess Controls Ltd. Page 7-19