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SYNPLIFY: Conditions of "Force GSR Usuage" - to generate the STARTUP block?


Record #4034

Problem Title:
SYNPLIFY:  Conditions of "Force GSR Usuage" - to generate the STARTUP
block?



Problem Description:
Keywords:  synplify, xc4000, xc5200, gsr, gr, startup

Urgency: Standard

General Description:  What are the conditions for which Synplify
will generate the STARTUP block?


Solution 1:

Synplify will generate the STARTUP block under the following
conditions:

(1) When *all* the FFs in the design have the same reset signal. This
is irrespective of whether "Force GSR Usage" is turned on or off.  By
default, if there is a single reset used in the design, then Synplify
will connect that reset signal to a STARTUP block.  It will do this even
if some flip-flops have no reset at all.

(2) When the design has some FFs with NO reset signal and some FFs with
reset signals and they all have the same reset signal. In this case,
"Force GSR Usage" will make a difference. You will not see GSR usage
unless you turn this option on.

To turn off the "Force GSR Usuage" option, choose "Set Device Options"
from the "Target" menu, and deselect the checkbox.



End of Record #4034