MC68HC05K1 FREESCALE [Freescale Semiconductor, Inc], MC68HC05K1 Datasheet - Page 30

• Manufacturer Part Number: MC68HC05K1
• Description: HCMOS Microcontroller Unit
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Technical Data
2.3 Input/Output Section
2.4 RAM
Technical Data
NOTE:
The first 32 addresses of the memory space, $0000–$001F, are the I/O
section. These are the addresses of the I/O control registers, status
registers, and data registers.
section.
The 32 addresses from $00E0 to $00FF serve as both the user RAM and
the stack RAM. The CPU uses five RAM bytes to save all CPU register
contents before processing an interrupt. During a subroutine call, the
CPU uses two bytes to store the return address. The stack pointer
decrements during pushes and increments during pulls.
Be careful when using nested subroutines or multiple interrupt levels.
The CPU may overwrite data in the RAM during a subroutine or during
the interrupt stacking operation.
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Memory
Figure 2-2
MC68HC05K0 • MC68HC05K1 — Rev. 2.0
is a register map of the I/O