MC68HC908AP16CFA MOTOROLA [Motorola, Inc], MC68HC908AP16CFA Datasheet - Page 53

• Manufacturer Part Number: MC68HC908AP16CFA
• Description: Microcontrollers
• Manufacturer: MOTOROLA [Motorola, Inc]

3.1 Introduction
3.2 Functional Description
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet – MC68HC908AP Family
NOTE:
NOTE:
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Section 3. Random-Access Memory (RAM)
This section describes the 2,048 (or 1,024) bytes of RAM.
Addresses $0060 through $085F (or $045F) 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 160 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, direct addressing mode instructions can
access efficiently 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.
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.
Be careful when using nested subroutines. The CPU may overwrite data
in the RAM during a subroutine or during the interrupt stacking
operation.
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
Data Sheet
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