MC68HC05E5 Datasheet, PDF (30/140 Pages) Freescale Semiconductor, Inc – General Release Specification

Freescale Semiconductor, Inc.
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.
Bit
Bit
12 11 10 9 8 7 6 5 4 3 2 1 0
0 00001
SP
Figure 3-6. Stack Pointer (SP)
3.7 Program Counter
The program counter is a 13-bit register that contains the address of the
next byte to be fetched.
Bit
12 11 10 9 8 7 6 5 4 3 2
PC
Figure 3-7. Program Counter (PC)
Bit
10
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.
General Release Specification
Central Processing Unit (CPU)
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MC68HC05E5 — Rev. 1.0