Answers Database

PPR 5.0,5.1: Possible cause of bad grouping using statements on TIMEGRP symbol


Record #530

Problem Title:
PPR 5.0,5.1: Possible cause of bad grouping using statements on TIMEGRP
symbol



Problem Description:



Solution 1:




PROGRAM: PPR

VERSION: 5.0, 5.1

PLATFORM: ALL

SHORT DESCRIPTION:

Forward - referencing TIMEGRP statements cause grouping errors

LONG DESCRIPTION:

PROBLEM:

Users may notice that, when using a TIMEGRP symbol to group symbols, that
the resulting groups are not what they expected, not containing the correct
number of symbols.

CAUSE:

One possible cause of this is the use of forward referencing statements in
TIMEGRP statements. For example, the following three lines could be added
to a TIMEGRP symbol:

	A=C
	B=FFS:EXCEPT:A
	C=RISING:FFS

A references C, and B references A, so therefore both A and B depend on C,
which is not yet defined. The software performs only one 'pass' to resolve
the references, so the A group ends up being defined correctly in this case,
but the B group would actually contain *all* flip-flops, since the A group
is empty when it is resolved.

SOLUTION:

Avoid these type of references in TIMEGRP statements.




End of Record #530