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Altera_Forum's avatar
Altera_Forum
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15 years ago

problem with cyclone III and jtag

I would like to put a very serious discussion about using jtag with cyclone III. has cyclone3 less electrical tolerance compared to other FPGA's?????? . we are building a custom board. and t...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
15 years ago

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You are right. They don't put the clamping diodes on figure 9-24, and instead recommend to use vcca (2.5V) as the jtag i/o power supply instead of the bank 3.0/3.3V supply. It works too, but I find the clamping diodes safer.

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Is it a problem to use VCCA 2.5V AND put something like the SN74LVC541 buffer in between the FPGA and JTAG connection? Do you advise that TCK, TMS, TDI, and TDO all go through the buffer.