Re: Connection for unused dual purpose pins of CPLD
OK. Thanks for your answer. I could not reply earlier as I was away on some work.
As I understand from the user guide, I can select one or more termination techniques from the software options. That’s fine if I don’t want to use any of the dual purpose pins. In that case, from hardware point of view, I can simply connect these pins to ground and then unselect the Xilinx software option – ‘use global output enable’, ‘use global set/reset’ etc. (picture attached for reference).
But suppose I want to use only one of the 4 global output enable pins of XC2C128 (VQ100 package). Then I would still have to keep the software option ‘use global output enable’ checked. In that case the remaining 3 pins will also work as global output enable pins. If I don’t want to use any other of these 3 pins in my hardware, will the unused pins get internally terminated as per the option selected (keeper -by default)? In this case what should I do with the pins in hardware – connect them to ground anyways? If I do connect them to ground, the outputs would get disabled. Isnt it? Hence, from PCB point of view, what should I do in this situation?
Also, if I want to use the remaining 3 pins as I/O pins, how can I do so? As I understand, they would be functioning as global output enable pins only.
Datasheet of XC2C128
here. Pinout of VQ100 on page 15.
Thanking You,
Hobbyiclearner.