Hi again,
Following up on my earlier post, I have come across another unusual timing problem. It seems I have timing paths that pass through flip flops. I've attached an example from the timing report. Using FPGA Editor to examine the implementation I have been able to confirm that oath addrRange and addrRange are flip flop outputs. In both cases the inputs seems to come through the carry logic, though and XOR gate, through a multiplexer to the D input of the flip flop.
Thanks in advance for your help.
-------------------------------------------------------------------------------- Slack: -2.537ns path ROBAVGSEG2/endAddr to ROBAVGSEG2/dataSum relative to 20.000ns delay constraint
Path ROBAVGSEG2/endAddr to ROBAVGSEG2/dataSum contains 10 levels of logic: Path starting from Comp: CLB_R22C54.S0.CLK (from CLK180) To Delay type Delay(ns) Physical Resource Logical Resource(s)
------------------------------------------------- -------- CLB_R22C54.S0.YQ Tcko 1.372R ROBAVGSE/eAddr ROBAVGSE/eAddr_reg CLB_R21C58.S1.F1 net (fanout=6) 2.258R ROBAVGSE/eAddr CLB_R21C58.S1.X Tilo 0.738R ROBAVGSE/syn6957 ROBAVGSE/C2679 CLB_R25C58.S1.G3 net (fanout=1) 1.633R ROBAVGSE/syn6957 CLB_R25C58.S1.Y Tilo 0.738R ROBAVGSE/C1432 ROBAVGSE/C2677 CLB_R25C58.S1.F3 net (fanout=2) 0.130R ROBAVGSE/syn6963 CLB_R25C58.S1.X Tilo 0.738R ROBAVGSE/C1432 ROBAVGSE/C2676 CLB_R23C55.S1.F4 net (fanout=16) 1.975R ROBAVGSE/C1432 CLB_R23C55.S1.X Tilo 0.738R ROBAVGSE/C1291/N21 ROBAVGSE/C2663 CLB_R24C59.S1.F1 net (fanout=1) 1.871R ROBAVGSE/C1291/N21 CLB_R24C59.S1.COUT Topcyf 1.445R ROBAVGSE/addrRange ROBAVGSE/C1281/C4/C0 ROBAVGSE/C1281/C4/C2 ROBAVGSE/C1281/C5/C2 CLB_R23C59.S1.CIN net (fanout=1) 0.000R ROBAVGSE/C1281/C5/C2/O CLB_R23C59.S1.Y Tciny 0.590R ROBAVGSE/addrRange ROBAVGSE/C1281/C6/C2 ROBAVGSE/C1281/C7/C1 CLB_R25C60.S1.F2 net (fanout=6) 1.577R ROBAVGSE/N7566 CLB_R25C60.S1.X Tilo 0.738R ROBAVGSE/syn2456 ROBAVGS2/C2558 CLB_R26C67.S0.G2 net (fanout=7) 1.766R ROBAVGSE/syn2456 CLB_R26C67.S0.Y Tilo 0.738R ROBAVGSE/C92/N85 ROBAVGSE/C2458 CLB_R21C75.S1.CE net (fanout=9) 2.544R ROBAVGSE/C92/N85 CLB_R21C75.S1.CLK Tceck 0.948R ROBAVGSE/dSum ROBAVGSE/dSum_reg
------------------------------------------------- Total (8.783ns logic, 13.754ns route) 22.537ns (to CLK180) (39.0% logic, 61.0% route)