xtcx
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errorar:228
For my FPGA(Spartan 3,speed grade -4) I have set the system clock speed of 100MHz.I never noticed any difference in my performance yet,but recently I noticed that at the end of the synthesis process,the ISE gives a tabulation which displays(approximately)
Timing Summary:
---------------
Speed Grade: -4
Minimum period: 24.976ns (Maximum Frequency: 40.038MHz)
Minimum input arrival time before clock: 9.585ns
Maximum output required time after clock: 7.484ns
Maximum combinational path delay: No path found something like that!. I think this is displayed at the last of synthesis.
I don't understand this!, the ISE still didn't complete implementation(routing,placing,etc) but how could it just report my maximum clk input is limited to some value?...Also this maximum clk speed limitation varies with different design!...Please clarify me why xilinx have stated 320MHz for spartan 3 chip clk speed,but why the synthesis process reports like this?.Is this due to the FF latency when cascading or due to the speed grade?....Thank you fellas!.
For my FPGA(Spartan 3,speed grade -4) I have set the system clock speed of 100MHz.I never noticed any difference in my performance yet,but recently I noticed that at the end of the synthesis process,the ISE gives a tabulation which displays(approximately)
Timing Summary:
---------------
Speed Grade: -4
Minimum period: 24.976ns (Maximum Frequency: 40.038MHz)
Minimum input arrival time before clock: 9.585ns
Maximum output required time after clock: 7.484ns
Maximum combinational path delay: No path found something like that!. I think this is displayed at the last of synthesis.
I don't understand this!, the ISE still didn't complete implementation(routing,placing,etc) but how could it just report my maximum clk input is limited to some value?...Also this maximum clk speed limitation varies with different design!...Please clarify me why xilinx have stated 320MHz for spartan 3 chip clk speed,but why the synthesis process reports like this?.Is this due to the FF latency when cascading or due to the speed grade?....Thank you fellas!.