Jim Brain wrote:
Michael J. Mahon wrote:What do you know! The decoding *is* done with a PLA after all!I don't think a PLA allows X (don't care) states. The large logic matrix at the bottom of the diagram is a wired-or matrix, which is why the illops exist.
In the area of processor design these days, a wired ROM decoder is often referred to as a PLA, since it is an array and it is "programmable" by wiring choices at design time. Wire-ORing is common to many logic configurations. -michael Music synthesis for 8-bit Apple II's! Home page: http://members.aol.com/MJMahon/ "The wastebasket is our most important design tool--and it is seriously underused."