Hi,eslapion wrote: ↑Sat May 06, 2017 1:01 amJust a word of warning concerning a PLA sub selling on eBay that also uses the XC9536XL: Me and Fredric have examined this product and we were curious as to why it would carry the 5ns version of that chip - PLAnkton carries the 10ns version.
Considering the speed of a C64 and that most other PLA substitutes have problems because they are actually too fast, there is absolutely no logical reason to use a faster chip that also turns out to be considerably more expensive - PLAnkton uses the 10ns version of the XC9536XL, it is the slowest and cheapest member of that family of chips and only it has the necessary characteristics to faithfully replicate the slow N82S100 on which the Commodore PLA was based.
Upon closer inspection, we have determined that the reason why the 5ns version was chosen is because it is in fact Chinese made counterfeits. Chinese clones of the XC9536XL are all marked as 5ns but they have all sorts of different response speeds. Also, on these counterfeit ICs the slew rate limiter as well as the low power mode don't operate properly. Of course, they are considerably cheaper than all genuine Xilinx XC9536XL, no matter what their rated speed may be.
I'm not happy about interfering to a thread where you you are trying to sell your product, but I think I have right to defend my product.
You are just guessing why I have used 5ns chip. The real reason is that by using 5ns chip I have a lot more possibilities adjusting the timing. If you would have measured the timing, you would have noticed that J-PLA doesn't have 5ns propagation delay, but instead about 25-30ns on every output, like the original 906114-01. Adjusting the delay can be made also on VHDL program, not just with an external RC-circuit.
I bought first CPLD's from China, but that doesn't mean they are counterfeits. I believe that they are genuine, but perhaps marked bad on the factory, sold to a dealer, who tested those again and found some to be working. Or maybe something else... impossible to know. Also possibly as good and genuine as the one's bought from authorized dealer. Anyway, I have tested those to have exactly same characterictics as the the one's bought from authorized dealer. Also the propagation delay is 5ns on every IC (as marked on top). All features, including slew rate limiter and low voltage modes work exactly as genuine, that's why I believe these to be genuine. I have also run very long test-routines on each J-PLA before selling them. But just to avoid any possible problems I decided to buy CPLD's about month ago from Digikey as well. And yes, these are the same 5ns versions also. So, all the latest I have sold and every item in the future will have CPLD bought from authorized distributor.