Re: Interesting 1970's IC

Posted by cadet1620 on Dec 31, 2011; 1:47am
URL: http://nand2tetris-questions-and-answers-forum.52.s1.nabble.com/Interesting-1970-s-IC-tp2673241p3622282.html

Here's the function table for the 74H87. Note L=FALSE, H=TRUE.

   Ctrl in |      Outputs
    -------------------------
     B  C  |  Y1  Y2  Y3  Y4
    -------------------------
     L  L  | !A1 !A2 !A3 !A4
     L  H  |  A1  A2  A3  A4
     H  L  |  H   H   H   H
     H  H  |  L   L   L   L

This chip implements 4 bits of the zx/nx circuit, so 4 of these chips would be needed for the x input processing. The B control input is the zx input; the C input is needs inverted nx. Y channel would require another 4 'H87s.

--Mark