Looking to use a CPLD. Which one to go for...?

[uncle_bob]

So if you want to use your fpga on a 5V bus then you will just have to 'bite the bullet' and install external buffers. In the old days such buffering was standard practice (even on purely 5V systems) because the bus driving capability of CPUs and peripheral chips was often very limited.

yes, I come from the 80s, I remember when I had to add a lot of 245 and 244 chips and then the PCB became more complex 

in my case, I might go for Spartan2, it's 5V tolerant, already successfully used in my Nintendo ADV (it's a project I made in 2003), but nowadays … I have difficulties in finding these chips

while it's almost easy to find a few XC95108 chips on Ebay, even if they are a bit expensive (10-20-30 euro),  apparently there is a little demand of these CPLD I guess because of their legacy feature and because they do not require external SPI flash which makes them perfect for "glue logic" in order to replace damaged chips in 5V systems

contrariwise it's difficult to see spartan2e chips, it smells they have zero demand 

Hi

As mentioned earlier, while it's easy to find some things "labeled" as this or that on eBay, it is not quite as easy to find good working examples of older parts. It's not just eBay. We occasionally get bit here at work exactly the same way. A taped up reel or tray comes in and ... surprise ... not what it's supposed to be. That's a major mess if you only catch it after they went through the pick and place.

Bob

[uncle_bob]

• the address lines need to be input only, in this project I do not need DMA
• the data lines need to be bidirectional
• ctrl lines is composed by 3 inputs, and 2 outputs

Hi

Ok, so address lines are simply 3.3V inverters / buffers / whatever that have 5V tolerant inputs. Same with the three control line inputs. That's 27 pins to deal with. It's either 14 pin packages at 6 to a package or something bigger with more PIA routing wise. I'd go with the 14 pin packages. The only real question then is "how small can you solder". If the five packages cost you more than 15 cents each, you need to shop harder (or stop buying DIP packages).

For the bidirectional pins, you can go the way I suggested earlier or there is another way:

For the "in" direction, it works just like the other inputs. For the "out" it's a tri-state 5V powered part with TTL level inputs. No resistors, no speed questions. Maybe a few more packages to deal with. Very simple to do.

Bob

[legacy]

about the PLL problem, currently I am using an external chip, MC88915 (and I am also ready with MC88916), it seems to me that Spartan 3E offered only 4 Digital Clock Managers (DCM) but did not offer any Phase-Locked Loops (PLL), while the Spartan 6 offers the more flexible CMT which provides both DCM's and PLL's!

so, I'd better use a Spartan 6 chip 

[uncle_bob]

about the PLL problem, currently I am using an external chip, MC88915 (and I am also ready with MC88916), it seems to me that Spartan 3E offered only 4 Digital Clock Managers (DCM) but did not offer any Phase-Locked Loops (PLL), while the Spartan 6 offers the more flexible CMT which provides both DCM's and PLL's!

so, I'd better use a Spartan 6 chip 

Hi

One of the "wonderful" debates when you get Xylinx and Altera guys at the same bar is the relative merits of the clock schemes used by each company. That is another layer on top of the whole "no fancy clock stuff in CLPD's" issue.

With both companies, the number of this and that (including clock inputs) goes up as the chips get bigger. The tendency is to advertise what is in the biggest million pad BGA in large type and put a unreadable footnote 22 pages later about the packages you can afford not having everything and anything in them. It's always best to do a bit of digging before you pick a specific chip. The data is there, it's generally in a nice table. That table probably is not in the first document you will come across.

Bob

[Artlav]

PLCC versions are getting rare, but adapter boards for TQFP packages are readily available.

On an off-topic note, where can i get one or what to look for?
Searching on both ebay and digikey produced zero results.
Google images do come up with something that kinda looks like one, but no actual links.

[nctnico]

PLCC versions are getting rare, but adapter boards for TQFP packages are readily available.

On an off-topic note, where can i get one or what to look for?
Searching on both ebay and digikey produced zero results.
Google images do come up with something that kinda looks like one, but no actual links.

Searching for 'qfp dip' on Ebay produces more than 200 results which prices starting from $1 including shipping.

[legacy]

it might depend on the area where one is located 

[nctnico]

Always search on Ebay.com ofcourse!

[Artlav]

Searching for 'qfp dip' on Ebay produces more than 200 results which prices starting from $1 including shipping.

Ah, ok.
I was looking for a QFP to PLCC adapter.
That is, something that would help program a tqfp44 CPLD in a programmer with a PLCC44 socket.

[Bruce Abbott]

I was looking for a QFP to PLCC adapter.
That is, something that would help program a tqfp44 CPLD in a programmer with a PLCC44 socket.

Such things are available, but they are not cheap!

You could make one from a tqfp programming socket and a PLCC plug like this, or perhaps even make the PLCC plug from scratch.



But there might be another way to do it that doesn't involve a PLCC plug.  Which programmer do you have, and what CPLDs do you want to program?
 

[nctnico]

Searching for 'qfp dip' on Ebay produces more than 200 results which prices starting from $1 including shipping.

Ah, ok.
I was looking for a QFP to PLCC adapter.
That is, something that would help program a tqfp44 CPLD in a programmer with a PLCC44 socket.

Usually only a few wires are needed for programming so it makes more sense to put a few pins on a board and solder these to a PLCC (or any other) socket.