pjd@demon.siemens.com (dr. funk) (11/05/90)
Greetings! We are just getting started with the latest release of irsim -- the one currently being distributed with Magic. We noticed that occasionally irsim will produce an X value in combinational logic that checks-out OK at the subsystem level. (That is, A, B and C are functionally correct, but A+B+C will produce some X's.) Yes, we have checked our connections -- several times :-) The problem appears to be related to the treatment of transmission gates in a multiplexer circuit. When we insert the functional equivalent of the MUX using the classic AND-OR gate form, our undefines go away. Two questions for the audience: 1. Does irsim have known problems with T-gates? 2. Are there rules (work-arounds) for irsim T-gates? Thanks, as they say, in advance. paul drongowski pjd@demon.siemens.com -- paul j. drongowski siemens corporate research inc pjd@demon.siemens.com