GAL G16V8 - complex expression

[dpatel]

Hi. I'm trying to a program a G16V8 using WinCUPL. I have 4 quite complex logic expressions - each with >8 product terms (which is the max allowed for this device). Is there a mode/CUPL technique that allows this to be implemented or is it just plain impossible?!

By the way I only have a couple of spare output pins left (if that makes any difference).

 

[lucbra]

any possibilities to split the expressions?
Why use this "old" device?

 

[dpatel]

I did think of using the feedback paths of the other pins but there aren't enough! Can't see how else to split the expression...

Unfortunately this is the device I have to use.

 

[FvM]

I don't understand what you are exactly asking for. Of course unused OLMCs can be utilized for the logic. You need to post the logic expressions to make us understand wheter they fit a 16V8.

I never used WinCUPL, but guess it can't split logic expressions without user interaction? An alternative way to find out if a give logic fits into the device is to use high level design tools like Lattice ispLEVER and a HDL logic description.

 

[dpatel]

I have 4 expression all similar to this:

yD = yD & X
# yD & !D
# yD & yA
# yD & yB
# yD & yC
# !yC & !yB & yA & X
# yC & !yB & !yA & X
# !yC & yB & !yA & X
# yC & !yB & !yA & H
# yC & yB & yA
# yD & yC & H & !yA
# yD & yC & !yB & H
# yD & !yC & X & yA
# yD & yB & X & !yA
# yD & yC & !yB & X;

 

[FvM]

The expression hasn't been minimized yet, many lines are obviously redundant.

 

[dpatel]

Sorry. Should have said the last few terms are added for static hazard cover. But I still have >8 terms.

 

[FvM]

O.K., then it can be implemented by utilizing two OLMCs, allowing 13 to 15 input terms, depending on the mode. tpd will be doubled.

 

[dpatel]

Thanks...

So, I would need 2 OLMCs for each expression like the one above? So, I would need 8 OLMCs in total for 4 complex expressions?

But I only have 3 spare output 'pins' for the extra OLMCs and I think that not all OLMCs can have feedback paths (if I've read the datasheet correctly) - correct???

What is tpd?

Sorry but I am very new to all of this!

 

[FvM]

But I only have 3 spare output 'pins' for the extra OLMCs and I think that not all OLMCs can have feedback paths (if I've read the datasheet correctly) - correct???

Yes if you also need output feedback for all terms or don't have 4 free OLMCs, the design isn't feasible. Presuming, you carefully checked for minimal number of terms.

 

[dpatel]

Thanks for the replies! I was re-reading the datasheet and wanted to ask if complex mode could do what I needed?

There are 10 inputs;
1 output (with it's own output logic)
and 4 logic expressions each with >8 product terms (as described above).

 

[FvM]

I don't think, that complex mode changes anything to the restricted resource "outputs with feedback option".