mc68hc908lj24 Freescale Semiconductor, Inc, mc68hc908lj24 Datasheet - Page 67

• Manufacturer Part Number: mc68hc908lj24
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

3.1 Contents
3.2 Introduction
3.3 Functional Description
MC68HC908LJ24/LK24 — Rev. 2.1
Freescale Semiconductor
Data Sheet — MC68HC908LJ24
NOTE:
NOTE:
Section 3. Random-Access Memory (RAM)
3.2
3.3
This section describes the 768 bytes of RAM (random-access memory).
Addresses $0080 through $037F are RAM locations. The location of the
stack RAM is programmable. The 16-bit stack pointer allows the stack to
be anywhere in the 64K-byte memory space.
For correct operation, the stack pointer must point only to RAM
locations.
Within page zero are 128 bytes of RAM. Because the location of the
stack RAM is programmable, all page zero RAM locations can be used
for I/O control and user data or code. When the stack pointer is moved
from its reset location at $00FF out of page zero, direct addressing mode
instructions can efficiently access all page zero RAM locations. Page
zero RAM, therefore, provides ideal locations for frequently accessed
global variables.
Before processing an interrupt, the CPU uses five bytes of the stack to
save the contents of the CPU registers.
For M6805 compatibility, the H register is not stacked.
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67
Random-Access Memory (RAM)
Data Sheet
67