quick question, interfacing 2 CPLD's together....

Hi, I've got 2 64 MC CPLD's, and I would like to be able to create designs for 128 macrocell devices. Assuming I can easily partition a design to fit on two chips, is there any special way I should 'physically'(or electrically) connect them? I mean, is it OK to simply connect, say, 8 I/O's from one to the other, assuming actual Inputs and Outputs are configured correctly? You see I'm designing a dev. board for these CPLD's and I don't want to order the PCB only to find out that I require a buffer or something. So, basically, is it ok to directly connect an I/O from one chip the I/O of another? Both chips being identical (MACH4A5-64/32)

It seems like a silly question, because Microcontrollers don't mind it, but I've had a couple of CPLD's that heated up quite badly when I connected them together.

Thanks

Buried(in)Code

As long as you actually connect outputs to inputs and not two outputs driving different levels there's no problem.

You could always have series resistors (100-1000 ohm or so) to limit the current in case you mess up and place outputs on the wrong pins.

Hi cyr, thanks for your reply!

Series resistors for currebt limiting probably would be a good idea, because I'm bound to set up the I/O's wrong at some point I'll add them to my design, thank god for SMT resistor networks

Thanks again man,

BuriedCode.