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Registered: ‎06-06-2011

JTAG daisy chain and standalone operation for a daughter board.

hello all,


i want to be able to interface a daughter board in both daisy chain(on the motherboard) and stand alone operation(one at a time) wrt JTAG.


meaning.......when i select the mode.....the daughter board should be a part of the daisy chain....and when not, it can be pulled out and can be used individually,with it's own JTAG connector.


one solution i have come up with is using a 2:1 MUX at the input TDIand one at the output TDO of the DAUGHTER board.


2:1 mux at TDI-- it can accept input from its own JTAG connector or from the previous TDO in the chain


1:2 mux at TDO-- where it can go back to the TDO of its own JTAG or the TDI of the next board in the daisy chain


but this is too specific.....i need a general solution.......for example if i just pick up any randon board and want to make it part of my chain.....what provisions will i have to make on my motherboard ?? is this even possible ??


any better solutions for this problem??




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Xilinx Employee
Xilinx Employee
Registered: ‎12-17-2007

Re: JTAG daisy chain and standalone operation for a daughter board.


It's possible but there are some issues to be aware of with JTAG bridges/muxes in general.

Please make sure to take a look at this Answer Record: http://www.xilinx.com/support/answers/16832.htm
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