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Altera_Forum
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15 years ago

MAX II JTAG pins for I/O logic

Hi, I've been wondering is it possible to use the JTAG port on MAX II CPLD to perform at the same time programming and usage of the pins for custom logic? The problem is that I have to use a 4 p...
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Altera_Forum
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15 years ago

You can connect 2 to 4 user pins in parallel to the JTAG pins and run a user protocol, that keeps the JTAG interface inactive, e.g. by not toggling TCK low. The user logic must keep the output pin tri-stated when it's idle and must not activate during normal JTAG operation. A 2 wire UART interface would be an option.