A small addition to the memory addressing logic is needed to support long word instructions. A new control signal MSW indicates that the most significant short word of a long word is being addressed, and forces the LSB of the address to 1.

We can now microcode the long-word variant of the Add instruction as follows.

# OPCODE L STAT : FETCH MASEL SHS EOI RFA1 WRF1 XSEL YSEL CMX AND CY1 CYP MSW

# Add Long
   11100 1 0001 :   0     1    0   0   010   1   01   10   0   0   0   0  0
   11100 1 0010 :   0     1    0   1   110   1   01   10   0   0   0   1  1

Add Long Test Video