Re: ASICs and PALs
salma ali bakr said:
what does functionality to I/O mean ???
A "high ratio of functionality to i/o" means that the application has LOTS of internal logic circuitry as compared to its number of i/o's. For example, consider a hypothetical application which performs real time fft conversions and has only the following i/o's:
* input: clock.
* input: serialized data stream from an a/d converter.
* input: adc frame marker.
* output: serialized fft output data.
* output: fft frame marker.
This application requires a bunch of mac units operating in parallel, along with serializer, deserializer and various other state machines. How many equivalent gates might that require? 100,000 or more? But it has only 5 i/o's! So this application might be a good fit for an asic because it has a large amount of internal logic compared to its i/o count.
Contrast the above device with a pal, which might have 20 i/o pins but substantially less internal logic than you would find in a typical asic. To implement the above application with pals might require hundreds of pal devices because each pal has a relatively small ratio of functionality (internal logic) to i/o count.