36
CHAPTER 4. INTERNAL CPU FUNCTIONS
4.5
ACCUMULATOR
In the
µ
PD75402A, the A register and the XA register pair function as accumulators. The 4-bit data process
instruction is executed mainly by the A register and the 8-bit data process instruction is executed mainly by the XA
register pair.
In the bit manipulation instruction, the carry flag (CY) functions as the bit accumulator.
Fig. 4-6 Accumulators
CY
X
A
Bit Accumulator
8-Bit Accumulator
A
4-Bit Accumulator