the cpld I use is a epm7032slc44, it has 4 vcc's and 4 gnd's. is it necessary to bind them together, or is it enough if I connect just one vcc and one gnd to the supply?
some vcc and some gnd pins are connected in chip,but you should connect all of them(vcc)to powersupply and all(gnd )pins to ground,
and don't forget to put 100nf capasitor between them.
Y its neccessary to tide each VCC an GND togather.... but for that u need to see the datasheet of the chip........Power requirements should be matched...
Peronally I observed that if it saying that VCC should be at 3.3V it may vary from 3 to 3.5V practically....
This VCC and GND is the core voltage of the chip... other VCC is for the IO bank of the chip...for outer interface...
It is a bad habbit not to tie all power pads to power signal even if all power pads are internally connect this can result in a more noise effect in your design especially if you are targetting a high speed requirements
part of it very relvant to what u want is following:
Powering and BypassingCPLDs require a lot of power in order to work correctly. Because of the amount of transistors, inputs,outputs, and whatnot crammed onto a square flake of silicon, CPLDs have multiple Vcc and GND pins.
In the .prt - file you can read how to connect all of the pins to the board. It's strongly recommended to do so. Otherwise you may get some diffuculties about designing your scheme.