ADD to AC
This instruction adds the content of the memory word specified by the effective address to the value of AC. The sum is transferred into AC and the output carry C,., is transferred to the E (extended accumulator) flip-flop. The rnicrooperations needed to execute this instruction are
DIT,: DR <--- M[AR]
D1T5: AC <--- AC + DR, E <--- C,.,, SC <--- 0
The same two timing signals, T, and T5, are used again but with operation decoder D1 instead of D0, which was used for the AND instruction. After the instruction is fetched from memory and decoded, only one output of the operation decoder will be active, and that output determines the sequence of rnicrooperations that the control follows during the execution of a memory-reference instruction.