Freescale Semiconductor MC68HC08KH12 Datasheet page 46

NOTE:
Advance Information
46
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.
MC68HC(7)08KH12 Rev. 1.1
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Freescale Semiconductor