I am an undergraduate student that working on a project which need to use an ispMACH 4256ZE CPLD to implement some data transfer function in my circuit.

Need someone whoever have worked with CPLD to answer two very basic question:

  1. For those gnd pins, do I need to connect all of them to ground? Or only some of them if I am using relative pins for in/out?

  2. I want to use external power instead of the usb power. I see three VCCO_3.3 pin so they should be connected to 3.3 v source. But what about three other pins called VCC_EXT, VCCO_EXT_0 AND VCCO_EXT_1. Should I just connect them to groud? And is there any other pin that I need to connect it to something for external power?



What you need is the data sheet(s) for the device. There are usually recommendations on how to make the various connections. Since your questions are "general," the answers can be provided by anybody that has electronics experience.
For your first question, yes, the gnd pins should all be connected to common ground (better to be safe).
For the second question, each of the VCC pins are for providing a different "hi level" voltage (5v, 12v), rather than the voltage provided to the chip (3.3v, 5v). If these pins are outputs that won't be used, then leave them unconnected.


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