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7470/7471/7477/7478 GROUP USER’S MANUAL

HARDWARE

1.7 Central processing unit (CPU)

1-23

1.7 Central processing unit (CPU)

The CPU of 7470/7471/7477/7478 group has the following 6 registers (referred as “CPU registers”).

q Accumulator (A) ························································· 8-bit

q Index register X (X) ··················································· 8-bit

q Index register Y (Y) ··················································· 8-bit

q Stack pointer (S) ························································ 8-bit

q Processor status register (PS) ································· 8-bit

q Program counter (PC) ············································· 16-bit

high-order (PCH) ·········· 8-bit

low-order (PCL) ············ 8-bit

Figure 1.7.1 shows a structure of CPU registers.

Fig. 1.7.1 Structure of CPU registers

Accumulator

Index Register X

Index Register Y

Stack Pointer

Program Counter

Processor Status Register (PS)

Carry Flag

Zero Flag

Interrupt Disable Flag

Decimal Mode Flag

Break Flag

Index X Mode Flag

Overflow Flag

Negative Flag

PCH

PCL

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