MC68HC05K0 Datasheet, PDF (38/154 Pages) Freescale Semiconductor, Inc – HCMOS Microcontroller Unit

Technical Data
Freescale Semiconductor, Inc.
3.3.3 Stack Pointer
The stack pointer (SP) shown in Figure 3-4 is a 16-bit register that
contains the address of the next location on the stack. During a reset or
after the reset stack pointer (RSP) instruction, the stack pointer initializes
to $00FF. The address in the stack pointer decrements as data is
pushed onto the stack and increments as data is pulled from the stack.
The 11 most significant bits of the stack pointer are permanently fixed at
00000000111, so the stack pointer produces addresses from $00FF to
$00E0. If subroutines and interrupts use more than 32 stack locations,
the stack pointer wraps around to address $00FF and begins writing
over the previously stored data. A subroutine call uses two stack
locations; an interrupt uses five locations.
Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 Bit 0
Read:
00000000111
Write:
Reset: 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1
Figure 3-4. Stack Pointer (SP)
Technical Data
MC68HC05K0 • MC68HC05K1 — Rev. 2.0
Central Processor Unit (CPU)
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