If you are using a PLL in the INTERNAL mode, make sure to use the PLL for frequency synthesis only. The PLL does not perform any phase-alignment or deskewing of the clock. Because of this, the phase relationship between the two clocks is not guaranteed and cannot be determined.
If the design requires that a known phase relationship be used with the PLL, use of the INTERNAL compensation mode is not recommended. In this case, use either SYSTEM_SYNCHRONOUS or SOURCE_SYNCHRONOUS, which have a known phase relationship between the input and output clock ports of the PLL.
Answer Number | 问答标题 | 问题版本 | 已解决问题的版本 |
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46790 | Spartan-6 FPGA Design Assistant - Troubleshooting Common Clocking Problems | N/A | N/A |
AR# 44706 | |
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日期 | 12/15/2012 |
状态 | Active |
Type | 综合文章 |
器件 |