All-
I am combining 2 .bit files into one .mcs for an XCF16P (XC3S1500-676 and XC3S1000-456). In both cases I've set the Configuration Rate parameterto 50. It takes 200 msec for DONE to go high -- that sounds too slow.
Can this be right? Which .bit file takes precedence? Is there something additional that needs to be set?
-Jeff
XCS1500 config is 5,214,784 bits XCS1000 config is 3,223,488 bits
( 5214784+3223488 bits ) / 50 MHz = 169ms (as a lower bound)
How much faster do you expect it to be?
Alan Nishioka
Alan-
Thanks for your reply.
The first FPGA has a PCI core. We were hoping to boot under 100 msec. Is there a way to go faster than 50 MHz without resorting to external clock + INIT gating circuitry?
-Jeff
I don't know. This is one of the reasons I have always used external pci bridges. But I thought there was more time during pci config.
All I can think of is using two config proms or using parallel config mode.
Alan Nishioka
On that line, what about one of the 150Mbit Winbond SPI memories, and a small CPLD to turn it into parallel-config ?
-jg
oops, that should be 150Mbd, of course....
Alan-
I looked up the PCI 2.3 spec, time to first config access is 2^25 clocks, or about 250 msec at 133 MHz. We have customers though who prize fast turn-on time, so I'm always looking to get under that 100 msec mark.
2 config proms? I wish. The board is jammed -- 16 layers, blind vias, lots of things like 201s and 2x3 mm oscillators. Pic of the board is here:Parallel config maybe... need to think about that.
-Jeff
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