Lattice XP2 daisy chain failed to program

[ryantran]

HI All,

I've been stuck on this problem for weeks and could not figure out why. I am unable to program 2 LFXP2-8E- PQFP208 connected in daisy chain on a prototype board.
I made sure TDI, TMS is pulled high with a 4.7K resistor and TCK is pulled low with a 68Ohm (I even tried adding another 47pF cap). Both are configured in Self-Download-Mode (CFG0 pin is set to 1). PROGRAMN, INITN, DONE are left floating. I'm using JTAG programmer TE0790-03L and Diamond Programmer. The Diamond Programmer was able to consistently scan 2 devices (with a warning that it cannot recognize the package). But when I start programming, sometimes I received the error "Failed to verify ID" during configuration setup. other times the JTAG chain verification pass, Erase pass but failed during program with errors "failed PROGRAM_STATUS" or "failed in READ_ID". So even the errors are not consistent.   Furthermore, on our system we have another MachXO2 sitting by itself having its own JTAG connector and I was able to flash the MachXO2 perfectly fine with the same hardware and software. So it can't be the JTAG programmer.

Before working on this prototype, I created a simple dummy board that has LFXP2-8E-PQFP208 and MacXO2-640UHC-144 connected in chain. Using exactly same JTAG programmer and software, I am ABLE TO consistently program the 2 FPGAs on this board without any problems. Of course I've been trying to match all configuration on this prototype with the dummy board. So I'm confused why it does not work in the case of 2 LFXP2 connected in chain.

Any suggestions are really appreciated! Thank you!
Huy

[mon2]

No direct experience with this setup but:

TCK is pulled low with a 68Ohm

sounds extremely aggressive. Remove this resistor and test again. Suggest 10k or higher if you wish to park this line in IDLE states. Fairly sure that JTAG TCK will be push-pull type so even this external resistor is of no value.