问答 #32457 - 11.1 Timing Known Issue - OFFSET IN with FALLING keyword appears to be off by a whole clock cycle
11.1 Timing Known Issue - OFFSET IN with FALLING keyword appears to be off by a whole clock cycle
| 问答编号# | 32457 |
| 型号 | SW-Timing Analyzer/TRCE |
| 最后更新日期 | 2009-04-20 00:00:00.0 |
| 记录状态 | Active |
| 关键词 | arrival time |
疑问描述
Keywords: arrival time
When I review my OFFSET IN with FALLING keyword, I notice the clock arrival time was a whole clock cycle off when compared with the OFFSET IN with RISING keyword.
In the timing report:
Rising Edge Clock Arrival: -2.051 ns (both setup and hold)
Falling Edge Clock Arrival: 12.949 ns (both setup and hold)
I thought the clock arrival times are supposed to be the same; when is this going to be fixed?
解决方案
The clock arrival times should be the same. This issue is caused by the negative phase-shifting performed in the DCM/PLL/MMCM components.To work around this problem, perform positive-phaseshifting; the clock arrival times will then be the same.
This issue is scheduled to be fixed in the next major release of the software.