Can CPLD be used to construct a clocked serial port for PIC

[nurquhar]

In thinking about my project described in http://www.ccsinfo.com/forum/viewtopic.php?t=32649 and I am wonder about CPLD's.

Could a CPLD be used to construct a high speed parallel to serial driver for the MAX6974 ? Essentiial it would need an 8 bit bus loaded FIFO buffer linked to a shift reg. Realy its simple synchronous serial port that could be run at a speed upto 31Mhz. Does anyone who knows about CPLD's know if what I describe might be possible ?

My other option might be to try stick a FIFO buffer chip on the front of a Shift Reg logic chip.

[Ttelmah]

Of course this could be done in a CPLD. It is not even terribly fast for most devices, or requiring that many gates.
The problem would actually be finding a small enough device, that you are not wasting 99% of it!...
Seriously though, if you have a CPLD, and this is all you are using it for this, then why not get rid of the PIC?. Complete PIC 'cores' are readily available to put into a CPLD device, and you could modify one to have the parallel output register directly mapped.

Best Wishes

[nurquhar]

Wow, a PIC in CPLD. Do I understand this correctly, I could have a say a 16F876A and a PLD all in the same chip ? Things in the PLD world have certainly moved on since I last used them 15 odd years ago for the trival task of address decoding on a 68K SBC. Can you suggest a manufacture/device I should start my researching from?

[Ttelmah]

Do a web search for 'opencores'. There are several open source PIC cores available, which will run directly in something like a Xilinx FPGA.
Look for the PPX16 core, which is a basic PIC16 core, with only a few basic peripherals. However the speeds make the standard PIC look so slow. In the Xilinx devices, you can be talking over 40mips...
Seriously the biggest change in recent years, has been the disappearance of small FPGA devices. Twenty years ago, there were small chips like the PALs. Though a few of these still exist, in the same size package now, and usually for lower cost, there are programmable logic devices with 10000 gates, versus the couple of hundred in the typical PAL. Even 15years ago, processor cores were available, but the FPGAs needed were quite large. Now quite complex cores can fit in fairly 'routine' devices. There are complete 16bit processor cores for some of the slightly larger arrays!...

Best Wishes