Answers Database

Bitgen 1.2: BUFGP sourced from internal logic may produce incorrect bitfile.


Record #2520

Product Family:  Software

Product Line:  Merged Core

Problem Title:
Bitgen 1.2: BUFGP sourced from internal logic may produce incorrect
bitfile.



Problem Description:
Keywords: bitgen, clock buffer, bufgp

Urgency: Hot

If you have the following arrangement for a 4000E:

 logic------>BUFGP------->logic

where the BUFGP is sourced from internal logic instead of
a pin, Bitgen 1.2.11 may produce a .bit file where the BUFGP does not pass the i
nput signal correctly.


Solution 1:

The following arrangement should work:

logic------->OBUF----x------->BUFGP------>logic
		     |
		     |
		    IOPAD

Note that this is logically the same as the above; this is how
a BUFGP is actually implemented in a 4000E device when it
is sourced by internal logic.

This should be corrected for the M1.3 release ( you should be
able to use the more concise logic-->bufgp-->logic
arrangement).





End of Record #2520