I was trying to use an SR flip flop in an ATF 1508 design and assumed that all that I would have to do was to
write logic equations for the .S and .R inputs and that WinCupl and the fitter would figure out the rest.

Note that Devhelp.pdf explicitly mentions the .S and .R extensions as being available on the 1508, thus:

However, when I try to use the .S and .R extensions, WinCupl gives me a warning that looks like this:

After some more digging I found a mention of an apparently almost completely undocumented keyword "register_select"
which appears to have something to do with explicitly telling WinCupl what type of flip flop you want to use.

"register_select" is used in the CONVERT.PLD example file but that really doesn't explain what it does:

Unfortunately I can't find any of that "more information" which is supposed to be available in the CUPL help menu
and randomly playing with the "register_select" keyword in my design along with the magic numbers 0, 1, 2 and 5
didn't appear to help.

Any ideas?

btw I realize that I don't really *need* an SR flip flop - I am currently just using the.AR and .AP inputs on a D flip
flop that has .D and .CK set to 0 and that works just fine, but I am curious if anyone knows how this is supposed to work.

Welcome!

I have no special knowledge, but did you also try with uppercase R and S? The message you quoted looks as if it is complaining about lowercase r and s.

Ed is echoing my thoughts. WinCUPL can be fussy about case.

_________________
x86?  We ain't got no x86.  We don't NEED no stinking x86!

Check the old version of CUPL reference:
https://www.qsl.net/bh1phl/CUPL_USERS_GUIDE.pdf

REGISTER_SELECT is on the page 61:



So it's actually a syntactic sugar for D-type expression. All code will be transferred to D-type expression.

I found on the 1504 that the AP and AR worked for asynchronous Preset and asynchronous Reset, which is very similar to S/R

Give those a try.

Daryl

_________________
Please visit my website -> https://sbc.rictor.org/

Here's an example from the SPIv2 code. Note I am using a D register, with a clocked function to reset the register during the active /RES of the CPU. Then use the AS/AR pair to actually switch the register states during operation.

Hope that helps.

Daryl

_________________
Please visit my website -> https://sbc.rictor.org/