Answers Database
2.1i Virtex Map - Eligible flop is not considered for input IOB merge.
Record #7888
Product Family: Software
Product Line: FPGA Implementation
Product Part: map
Product Version: 2.1i
Problem Title:
2.1i Virtex Map - Eligible flop is not considered for input IOB merge.
Problem Description:
Urgency: Standard
General Description:
An FDCE with IOB=TRUE is driven by IBUF, but is not merged into the input register of an IOB.
This appears to be because it is also being considered for and rejected for an output register merge
.
The flop drives an inverter which in turn drives an OBUFT (same IOB).
Solution 1:
Work Around: A KEEP property on the net between the inverter and OBUFT, results in the
FDCE being merged into the input register.
INST "$I22/$1I15" IOB = TRUE ;
NET "$Net00002_" KEEP ;
A CR is pending for this issue.
End of Record #7888 - Last Modified: 10/18/99 15:27 |
