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AR# 3092

Foundation F1.3 State Editor: when selecting HOLD for Unsatisfied Conditions, selection not kept.

Description

Keywords: state editor, fsm, undefined, hold

Urgency: Standard

General Description:
In F1.3 State Editor, using VHDL encoding, when user edits
Unsatisfied Conditions to be handled as a HOLD:
(RClick w/in State Machine window -> Properties -> Defaults ->
Unsatisfied Conditions),
the HOLD selection appears to be accepted. But if the user goes
back into the same window after applying HOLD to the state
machine, the selection has changed to Don't Care. In F1.3 State
Editor-VHDL encoding, when user edits Unsatisfied Conditions to
be handled as a HOLD (RClick w/in State Machine window ->
Properties -> Defaults -> Unsatisfied Conditions), the HOLD
selection appears to be accepted. But if user goes back into
same window after applying to state machine, the selection has
changed to Don't Care.

Solution

In VHDL, the two choices, HOLD and Don't Care, have the same functionality. The HOLD choice, if fully implemented, would add a line to each 'case' choice:
case State_machine is
when S1 =>
if i=1 then
State_machine <= S2;
else
State_machine <= S1; --This line is due to HOLD

when S2 =>
...

The line introduced by HOLD is redundant. Without it, the same action is implied. F1.3 writes the VHDL code the same, regardless of the two choices.

The problem does not occur in ABEL encoding.
AR# 3092
Date Created 11/17/1997
Last Updated 03/02/1999
Status Archive
Type General Article