The algorithm for Twos Complement Multiplication is as follows:

Step 1: Load multiplicand in MD, multiplier in MR. For negative numbers, two’s complement format to be used.

Step 2: Initialize the down counter CR by the number of bits involved.

Step 3: Clean locations PD (n-bits) and Mx (1 –bit).

Step 4: Check LS bit of MR and Mx jointly. If the pattern is 00 or 11 then go to Step 5. If 10, then PD - PD - MD. If 01, then PD - PD + MD.

Step 5: Perform arithmetic right-shift with PD, MR and Mx. LS of PD goes to MS of MR and LS of MR goes to Mx. Old content of Mx is discarded

Step 6: Decrement CR by one. If CR is not zero then go to Step 4.

Step 7: Final result (or the product) is available in PD (higher pan) and MR (lower part).