Freescale Semiconductor, Inc.
Advance Information — MC68HC908RFRK2
Section 3. Random-Access Memory (RAM)
3.1 Contents
3.2
3.3
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41
3.2 Introduction
This section describes the 128 bytes of random-access memory (RAM).
3.3 Functional Description
Addresses $0080–$00FF are RAM locations. The location of the stack
RAM is programmable.
NOTE: For correct operation, the stack pointer must point only to RAM
locations.
Before processing an interrupt, the CPU uses five bytes of the stack to
save the contents of the CPU registers.
NOTE: For M68HC05, M6805, and M146805 compatibility, the H register is not
stacked.
During a subroutine call, the CPU uses two bytes of the stack to store
the return address. The stack pointer decrements during pushes and
increments during pulls.
NOTE: Be careful when using nested subroutines. The CPU could overwrite
data in the RAM during a subroutine or during the interrupt stacking
operation.
MC68HC908RFRK2
MOTOROLA
Advance Information
41
Random-Access Memory (RAM)
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