mc68hc11f1cpu3 Freescale Semiconductor, Inc, mc68hc11f1cpu3 Datasheet - Page 26

• Manufacturer Part Number: mc68hc11f1cpu3
• Description: Mc68hc11f1 Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

3.1.1 Accumulators A, B, and D
3-2
Accumulators A and B are general-purpose 8-bit registers that hold operands and re-
sults of arithmetic calculations or data manipulations. For some instructions, these two
accumulators are treated as a single double-byte (16-bit) accumulator called accumu-
lator D. Although most instructions can use accumulators A or B interchangeably, the
following exceptions apply:
The ABX and ABY instructions add the contents of 8-bit accumulator B to the contents
of 16-bit register X or Y, but there are no equivalent instructions that use A instead of B.
The TAP and TPA instructions transfer data from accumulator A to the condition code
register, or from the condition code register to accumulator A, however, there are no
equivalent instructions that use B rather than A.
The decimal adjust accumulator A (DAA) instruction is used after binary-coded deci-
mal (BCD) arithmetic operations, but there is no equivalent BCD instruction to adjust
accumulator B.
15
15
15
15
15
CONDITION CODE REGISTER
Freescale Semiconductor, Inc.
For More Information On This Product,
DOUBLE ACCUMULATOR D
Figure 3-1 Programming Model
PROGRAM COUNTER
INDEX REGISTER X
INDEX REGISTER Y
STACK POINTER
CENTRAL PROCESSING UNIT
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S
7
7
7
X
6
H
ACCUMULATOR A
ACCUMULATOR B
5
4
I
N
3
2
Z
V
1
C
0
0
0
0
0
0
0
0
A
B
D
IX
IY
SP
PC
CCR
CARRY
OVERFLOW
ZERO
NEGATIVE
I INTERRUPT MASK
HALF-CARRY (FROM BIT 3)
X INTERRUPT MASK
STOP DISABLE
TECHNICAL DATA
MC68HC11F1