Answers Database
XC2000/XC3000/XC4000/XC5200: What set, reset capabilities do the 2000. 4000, 5200 flip flops have?
Record #151
Problem Title:
XC2000/XC3000/XC4000/XC5200: What set, reset capabilities do the 2000. 4000, 5200 flip flops
have?
Problem Description:
Keywords
Solution 1:
Due to architectural differences in the flip flops in the 2, 3, and 4k families of devices, the same
set and reset abilities are not available to them all;
2000: FFs can both set and reset asynchronously.
3000: FFs can only reset asynchronously.
4000E/EX/XL/XV: FFs can either set OR reset asychronously, but not both.
3000: Latches are not reliable because of potential timing
issues. User should be aware min timing specs are not
specified.
4000e: Latches maybe safely implemented using RAM. Look at
solution 122 for more details. However, the ones present in
the library may have the same problems as the XC3000.
4000ex/xl/xv: The CLBs in these devices contain latches and
can be safely used.
End of Record #151 - Last Modified: 09/10/97 15:37 |
