Panasonic MN101C77C User Manual

II - 7

Chapter 2 CPU Basics

Overview

Address Registers (A0, A1)

These registers are used as address pointers specifying data locations in memory. They support the

operations involved in address calculations (i.e. addition, subtraction and comparison). Those pointers

are 2 bytes data. Transfers between these registers and memory are always in 16-bit units. Either odd or

even address can be transferred. At reset, the value of address register is undefined.

Stack Pointer (SP)

This register gives the address of the byte at the top of the stack. It is decremented during push opera-

tions and incremented during pop operations. Ar reset, the value of SP is undefined.

2-1-6

Registers for Data

Registers for data include four data registers (D0, D1, D2, D3).

Data Registers (D0, D1, D2, D3)

Data registers D0 to D3 are 8-bit general-purpose registers that support all arithmetic, logical and shift

operations. All registers can be used for data transfers with memory.

The four data registers may be paired to form the 16-bit data registers DW0 (D0+D1) and DW1 (D2+D3).

At reset, the value of Dn is undefined.

Address Registers

Stack Pointer

8 7

DW0

DW1

Data
registers