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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

What voltage are you using for the JTAG interface? There is an issue when you use 3.0 or 3.3V for the Jtag signals, if you don't add external clamping diodes. If an overshoot voltage goes over 4.1V it can destroy the I/O buffer of the FPGA.

Usually if I have the space I put a buffer on the PCB between the FPGA and the JTAG connector, for protection.