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 pin connector + the supply voltages for both programming and communication with the CPLD. So, any suggestions? Thanks in advance Best regards, VT
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.