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XC5200: BUFG - different skew between clock pin and non clock pin.Record #1305
Product Family: Hardware XC5200: BUFG - different skew between clock pin and non clock pin. Problem Description: The BUFG of the XC5200 family of devices drives clock signal to the flip-flops. A low skew is guaranteed, typically less than 1ns. The BUFG of the XC5200 family is also capable of driving non clock signals such as CE or LUT (Look-up Table) inputs . The skew between CLBs that are in the same column is still low. However the skew between the CLBs placed in different columns can increase if the fanout and/or the type of loading on the vertical longline related to this global signal is differs from one column to another. For instance : BUFG drives a signal 'global'. The signal 'global' is connect- ed to CE of CLB_R1C1, CLB_R2C1, CLB_R3C1, and CLB_R1C2, and also to LC0.F2 of CLB_R4C1, CLB_R5C1, and CLB_R6C1. The skew on 'global' between CLBs in column 1 and CLBs in column 2 could be greater than 1ns. Solution 1: Having the same fanout/load on each vertical longline, can reduce clock skew. End of Record #1305 - Last Modified: 05/28/97 16:26 |
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