MC68HC705JJ7 Datasheet, PDF (29/164 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 3
Central Processor Unit (CPU)
3.1 Introduction
This section describes the central processor unit (CPU) registers. Figure 3-1 shows the five CPU
registers. CPU registers are not part of the memory map.
7
0
A
ACCUMULATOR (A)
7
0
X
INDEX REGISTER (X)
15
65
0
0000000011
SP
STACK POINTER (SP)
15
10
87
0
111
PCH
PCL
PROGRAM COUNTER (PC)
7
54
0
1 1 1 H I N Z C CONDITION CODE REGISTER (CCR)
HALF-CARRY FLAG
INTERRUPT MASK
NEGATIVE FLAG
ZERO FLAG
CARRY/BORROW FLAG
Figure 3-1. M68HC05 Programming Model
3.2 Accumulator
The accumulator is a general-purpose 8-bit register as shown in Figure 3-2. The CPU uses the
accumulator to hold operands and results of arithmetic and non-arithmetic operations.
Bit 7
Read:
Write:
Reset:
6
5
4
3
2
Unaffected by reset
Figure 3-2. Accumulator (A)
1
Bit 0
MC68HC705JJ7 • MC68HC705JP7 Advance Information Data Sheet, Rev. 4.1
Freescale Semiconductor
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