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JTAG and SPROM for Spartan II-e

I'm currently laying out a PCB containing a Spartan II-E (XC2S200E PQ208). I'm laying out the circuitry for an SPROM chip to store my bit file, but due to time constraints I would like to be able to program the chip using the JTAG interface (similiar to the one on the development board I am using, a Digilent development board from NuHorizons) in case, due to time constraints, I am unable to program the SPROM before a presentation.

I'm familiar with the way the JTAG cable works but am a little confused as to how the four pins (TMS TDI TDO TCK) interact with the FPGA. Based on my knowledge, I am assuming that the four pins are wired one to one with the corresponding FPGA input pins (and one output). The board I'm using has a parallel port to JTAG interface which makes tracing the port routes confusing. I really only have one or at most two shots at the PCB so I was just wondering if the JTAG pins can be wired directly to the FPGA, no buffer chip or anything in their way.

Thanks!

George

Reply to
aosik5
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confused

The Xilinx Platform Flash data sheet shows the connections required. TMS, and TCK are wired in parallel to all devices in the JTAG chain. TDI and TDO form a loop where the TDO of each device in the chain connects to the TDI of the next device. Normally the SPROM is in the chain before the FPGA it programs, but this isn't necessary. The Platcorm Flash datasheet also shows the serial connections from the SPROM to the FPGA for boot time loading in master serial mode.

See figure 8 in:

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Reply to
Gabor 

--
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/ /\/\ Aurelian Lazarut
\ \  / System Verification Engineer
/ /  \ Xilinx Ireland
\_\/\/
 
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Aurelian Lazarut

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