Motorola MC68HC05RC8 User Manual
Central Processor Unit
General Release Specification
MC68HC05RC16 — Rev. 3.0
34
Central Processor Unit
MOTOROLA
Figure 3-2. Stacking Order
3.3 Accumulator
The accumulator (A) is a general-purpose 8-bit register used to hold
operands and results of arithmetic calculations or data manipulations.
operands and results of arithmetic calculations or data manipulations.
3.4 Index Register
The index register (X) is an 8-bit register used for the indexed
addressing value to create an effective address. The index register also
may be used as a temporary storage area.
addressing value to create an effective address. The index register also
may be used as a temporary storage area.
INDEX REGISTER
PCL
ACCUMULATOR
CONDITION CODE REGISTER
PCH
1
1
1
7
0
STACK
I
N
T
E
E
R
R
U
P
R
U
P
T
DECREASING
UNSTACK
R
E
E
T
U
R
N
R
N
INCREASING
NOTE:
Since the stack pointer decrements during pushes, the PCL is stacked first,
followed by PCH, etc. Pulling from the stack is in the reverse order.
followed by PCH, etc. Pulling from the stack is in the reverse order.
MEMORY
ADDRESSES
MEMORY
ADDRESSES
7
0
A
7
0
X