HC705E5GRSSLASHD datasheet(32/148 Pages) NXP

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Central Processing Unit (CPU)

General Release Specification

MC68HC705E5 — Rev. 1.0

Central Processing Unit (CPU)

3.6 Stack Pointer

The stack pointer 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 then is

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

is pulled from the stack.

When accessing memory, the seven most significant bits (MSB) are

permanently set to 0000011. These seven bits are appended to the six

least significant register bits to produce an address within the range of

$00FF to $00C0. 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.

3.7 Program Counter

The program counter is a 13-bit register that contains the address of the

next byte to be fetched.

NOTE:

The HC05 CPU core is capable of addressing 16-bit locations. For this

implementation, however, the addressing registers are limited to an

8-Kbyte memory map.

Bit

987654321

Bit

0001

Figure 3-6. Stack Pointer (SP)

Bit

987654321

Bit

Figure 3-7. Program Counter (PC)

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

HC705E5GRS/D Datasheet(PDF) 32 Page - NXP Semiconductors