edavio
Member level 3
max trace lenght for pci signal
According PCI specs, there has max trace length constrain for pci signal on expansion card. It say that pci signal trace on expansion must less than 1.5 inch. I am confusing why it has this constrain. Is it because of timing issue or signal integrity issue? 33Mhz PCI have 10 ns timing budget for propagation delay. Base on my understanding, the signal trace can be as long as 60 inch(as signal speed is 6 inch/ns). It is far beyond 1.5 inch. even, we think about trace on planar board. If I assume that the trace on planar board consume 30 inch, I think it still should has 30 inch trace length budget on expansion board (60 - 30 = 30).
Pls advise!
According PCI specs, there has max trace length constrain for pci signal on expansion card. It say that pci signal trace on expansion must less than 1.5 inch. I am confusing why it has this constrain. Is it because of timing issue or signal integrity issue? 33Mhz PCI have 10 ns timing budget for propagation delay. Base on my understanding, the signal trace can be as long as 60 inch(as signal speed is 6 inch/ns). It is far beyond 1.5 inch. even, we think about trace on planar board. If I assume that the trace on planar board consume 30 inch, I think it still should has 30 inch trace length budget on expansion board (60 - 30 = 30).
Pls advise!