Freescale Semiconductor, Inc.
Ce ntra l Proc e ssor Unit (CPU)
3.2 Introd uc tion
This section describes the CPU registers. Figure 3-1 shows the five
CPU registers. CPU registers are not part of the memory map.
7
0
0
0
0
A
X
ACCUMULATOR (A)
7
INDEX REGISTER (X)
15
0
6
1
5
0
1
0
1
0
0
0
0
0
8
1
7
SP
STACK POINTER (SP)
15
1
10
PCH
PCL
PROGRAM COUNTER (PC)
CONDITION CODE REGISTER (CCR)
7
1
5
1
4
0
1
H
I
N
Z
C
HALF-CARRY FLAG
INTERRUPT MASK
NEGATIVE FLAG
ZERO FLAG
CARRY/BORROW FLAG
Figure 3-1. 68HC05 Programming Model
3.3 Ac c um ula tor (A)
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
6
5
4
3
2
1
Bit 0
Read:
Write:
Reset:
Unaffected by Reset
Figure 3-2. Accumulator (A)
General Release Specification
MC68HC705JJ7/MC68HC705JP7 — Rev. 3.0
Central Processor Unit (CPU)
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