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Altera_Forum's avatar
Altera_Forum
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15 years ago

JTAG and/or IO pin usage

Hello all, I'm new to CPLDs but I'm very keen on getting a little project up and running soon. The basic question is: is it possible to program a EPM3064 through the JTAG pins, then use th...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
15 years ago

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I'll just treat the JTAG port as if it's always a JTAG port then, and double-up the JTAG connections to spare IO (which I have heaps of) and be done with it - easy!

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???

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If JTAG can't be reenabled easily I won't bother disabling it.

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Unselect the "Enable JTAG BST support" option in "Device and Pin Options/General Tab". Then the four JTAG pins are available for assignment as general I/O.

I agree, that the description of this feature in the device hardware manual isn't particularly clear. I didn't try it yet, but it's obvious to me, that the JTAG functionality can't be re-enabled with standard low voltage levels, otherwise the usability of the respective I/O pins would be restricted.