How to obtain (accurate) critical path delay?

Jul 16, 2007 0 Replies

Dear



Asking many questions on this board --:



My goal is to get "critical path delay" (or maximum clock frequency) of simple "register file", as described in the following :


--------------------------- There is a register. Before register, there is a combinational logic. After register, there is a combinational logic.



---------------------------



I obtained following 5 different reports. My question is that which report (ouf of (1),(2),(3a),(3b),(3c) ) represents the most accurate "critical path delay" of my implementation?



(1) Synthesis report reports :



--------------------------- Minimum period: No path found Minimum input arrival time before clock: 4.026ns Maximum output required time after clock: 4.636ns Maximum combinational path delay: 5.975ns



---------------------------



(2) Asynchronous delay report reports :



--------------------------- The 20 worst nets by delay are: | Max Delay | Netname | 9.579 ReadRegister1_0_IBUF 8.965 SelectRC_IBUF 8.524 ReadRegister2_0_IBUF .......



---------------------------



(3) Post Place & Route Static Timing report reports :



--------------------------- (3a)Pad to Pad



-------------------------- Source Pad |Destination Pad| Delay | ReadRegister1|ReadData1 | 10.063| ReadRegister1|ReadData1 | 12.041| ...


--------------------------- (3b) Clock clock to Pad



--------------------------- | clock | | clock | Destination | to PAD |Internal Clock(s) | Phase | ReadData1 | 9.365(R)|clock_BUFGP | 0.000| ReadData1 | 9.557(R)|clock_BUFGP | 0.000| ReadData1 | 9.465(R)|clock_BUFGP | 0.000| ........



--------------------------- (3c) Setup/Hold to clock clock



--------------------------- | Setup to | Hold to | | Clock | Source | clk (edge) | clk (edge) |Internal Clock(s) | Phase | SelectRC | 13.663(R)| -1.584(R)|clock_BUFGP |



0.000| WriteData | 3.373(R)| -0.104(R)|clock_BUFGP |
0.000| WriteData | 2.466(R)| 0.711(R)|clock_BUFGP |
0.000| ........

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