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Altera_Forum
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18 years ago

Running into infinite loop problems

I'm relatively new to Quartus and I'm trying to define a latch with three outputs and the following properties: L M | Q(t+1) | R(t+1) | S(t+1) ------------------------------ 0 0 | S(t) ...
Altera_Forum's avatar
Altera_Forum
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18 years ago

I missed this when I first looked at the code, but I'm not sure what is supposed to happen when L=0 and M=0. I thought everything just held their values(like a latch does), but they hold someone else's value, in a roundabout way. Conceptually, a latch is an output that feeds back on itself and into a mux(the select line of the mux is the latch's gate). What you're describing is a cross-connect and I'm not surprised they start toggling.

Ignoring the other states, in this condition you have three nodes where Q <= S <= R <= Q <= S <= R <= etc., i.e. something that will toggle unless S = Q = R.