MC68HC705MC4MP datasheet(37/180 Pages) FREESCALE

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Central Processing Unit

Stack Pointer

General Release Specification

Central Processing Unit

N — Negative

When set, this bit indicates that the result of the last arithmetic, logical,

or data manipulation was negative.

Z — Zero

When set, this bit indicates that the result of the last arithmetic, logical,

or data manipulation was zero.

C — Carry/Borrow

When set, this bit indicates that a carry or borrow out of the arithmetic

logical unit (ALU) occurred during the last arithmetic operation. This

bit is also affected during bit test and branch instructions and during

shifts and rotates.

3.6 Stack Pointer

The stack pointer (SP) contains the address of the next free location on

the stack. During an MCU reset or the reset stack pointer (RSP)

instruction, the stack pointer is set to location $00FF. The stack pointer

is then decremented as data is pushed onto the stack and incremented

as data is pulled from the stack.

When accessing memory, the six most significant bits are permanently

set to 000011. These six bits are appended to the six least significant

Subroutines and interrupts may use up to 64 (decimal) locations. If 64

locations are exceeded, the stack pointer wraps around and loses the

previously stored information. A subroutine call occupies two locations

on the stack; an interrupt uses five locations.

000011

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MC68HC705MC4MP Datasheet(PDF) 37 Page - Freescale Semiconductor, Inc