MC68HC05L16 Datasheet, PDF (35/146 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 3
Central Processor Unit (CPU)
3.1 Introduction
This section describes the central processor unit (CPU).
3.2 CPU Registers
The MCU contains five registers as shown in Figure 3-1. The interrupt stacking order is shown in
Figure 3-2.
7
A
0
ACCUMULATOR
7
15
PC
15
7
00 0 0 0 0 0 0 11
X
SP
0
INDEX REGISTER
0
PROGRAM COUNTER
0
STACK POINTER
CCR
H
I NZC
CONDITION CODE
REGISTER
Figure 3-1. Programming Model
INCREASING
MEMORY
ADDRESSES
7
0 _STACK
1 11
CONDITION CODE
REGISTER
R
E
ACCUMULATOR
T
U
INDEX REGISTER
R
N
PCH
PCL
I
N
T
E DECREASING
R
MEMORY
R ADDRESSES
U
P
T
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
MC68HC05L16 • MC68HC705L16 Data Sheet, Rev. 4.1
Freescale Semiconductor
35