SPLDs

[laroche73]

Hi, everyone. Does anyone know of a site where I can find some information on the programming algorithms used to program simple programmable logic devices, like PEELs, ATF750s or GAL16V8s? It seems to be a well-guarded industry secret. ISP makes devices much easier to program, but it's only offered on moderate to high density PLDs that have enough pins to justify it. There are many designs where a smaller PLD would do (or where the smaller form-factor is preferred). Short of buying an expensive PLD programmer, I'll end up using the higher density devices, just for the ISP feature. Any ideas?

 

[crust]

without reading the whole document **broken link removed** seems to provide the answer.

 

[laroche73]

Thanks, that's more info than I've been able to find.

 

[laroche73]

programming small PLDs

Here's an update for those interested in programming small programmable logic devices that don't have ISP capability.

http://www.geocities.com/ResearchTriangle/Forum/8070/galblast.htm

describes a simple GAL programmer that works off a PC parallel port, and includes the software and hardware details.

**broken link removed**

is where I found the GALblast link and also has a link to a RS232-based GAL programmer design (the design can be downloaded as a ZIP file, the authors' homepage seems to be gone).

And here's a link for the programming algorithms used in PEEL devices (a better choice than GALs/PALs):

**broken link removed**

(The PA7xxxx links don't work, but the older PEEL device algorithms can be downloaded)

My personal opinion - It's doubtful whether it's still worth using the non-ISP devices if you don't have access to a commercial PLD programmer. A 3.3V Xilinx 9536 currently lists for $1.62 ($1.07@100 qty) at Digi-Key, vs. a PEEL 22V10 replacement at Jameco going for $2.59/($1.65/100). The 9536 is a far more capable PLD, and is in circuit re-programmable. It just seems like overkill for many simple designs. - Claude