MC68HC05C8A Datasheet, PDF (27/116 Pages) Motorola, Inc – Microcontrollers

Chapter 3
Central Processor Unit (CPU)
3.1 Introduction
This section describes the central processor unit (CPU) registers.
3.2 CPU Registers
The five CPU registers are shown in Figure 3-1 and the interrupt stacking order in Figure 3-2.
7
A
0 ACCUMULATOR
7
12
PC
12
7
0 0 0 0 0 11
X
SP
0
INDEX REGISTER
0
PROGRAM COUNTER
0
STACK POINTER
CCR
H INZC
CONDITION CODE REGISTER
Figure 3-1. Programming Model
7
0 _STACK
INCREASING
MEMORY
ADDRESSES
1
R
E
T
U
R
N
1 1 CONDITION CODE REGISTER _I
N
ACCUMULATOR
T
E
INDEX REGISTER
R
R
PCH
U
P
PCL
T
DECREASING
MEMORY
ADDRESSES
UNSTACK
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.
Figure 3-2. Stacking Order
MC68HC05C8A • MC68HCL05C8A • MC68HSC05C8A Data Sheet, Rev. 5.1
Freescale Semiconductor
27