Answers Database
XC3000A, XC4000/E/X: How to implement flip-flops with both asynchronous preset and clear/reset inputs
Record #2632
Product Family: Hardware
Product Line: 4000E
Product Part: 4000E
Problem Title:
XC3000A, XC4000/E/X: How to implement flip-flops with both asynchronous preset and
clear/reset inputs
Problem Description:
Urgency: standard
General Description:
The Xilinx XC3000/A/L and XC4000/E/EX/XL architectures do not
support flip-flops with both PRESET and RESET inputs. How
do you implement this functionality?
Solution 1:
Since neither architecture supports flip-flops with both SET
and RESET pins, there is no efficient way to implement such
a function. The best one can do is mimic such a configuration, using two flip-flops (one with a dir
ect PRESET
input, and the other with a direct RESET input) in
conjunction with a MUX which you would use to select the
appropriate flop, depending on which function was desired at
any given time.
The selection of PRESET or RESET functionality could
be controlled by the MUX control input.
End of Record #2632 - Last Modified: 03/02/99 18:08 |
