Section 8.4: An instruction in micro-detail (Frame 3)                     [prev][home][next]

Following is the sequence of control point assignments that accomplishes this. Each line of the following represents a distinct time step, and all the control points on the same line are turned on (or off) simultaneously. In those cases where a group of wires have the same names, such as the MAR-MUX wires (both 1 and 0), their individual names have been elided so as to save space. Thus, MAR-MUX=10 is shorthand for MAR-MUX1=1 and MAR-MUX0=0. Assume that all control wires contain 0 before step 1.

      1.     MAR-MUX=01
      2.     MAR-LD=1
      3.     MAR-LD=0;  MA=1;  WR=0;  MBR-MUX=10
      4.     MBR-LD=1
      5.     MBR-LD=0;  MA=0;  PC-INCR=1;  IR-LD=1
      6.     IR-LD=0;  PC-LD=1
      7.     PC-INCR=0;  PC-LD=0
      8.     MAR-MUX=00
      9.     MAR-LD=1
     10.     MAR-LD=0;  MA=1;  WR=0;  MBR-MUX=10
     11.     MBR-LD=1
     12.     MBR-LD=0;  MA=0
     13.     TMP-LD=1
     14.     TMP-LD=0;  F=101;  SH=00
     15.     A-MUX=00
     16.     A-LD=1
     17.     A-LD=0