MC68HC05RC8 Datasheet, PDF (36/122 Pages) Freescale Semiconductor, Inc – General Release Specification

Freescale Semiconductor, Inc.
Central Processor Unit
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 seven most significant bits 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.
13
7
0
0
0
0
0
1
1
0
SP
3.7 Program Counter
The program counter (PC) is a 13-bit register that contains the address
of the next byte to be fetched.
13
0
PC
NOTE:
The HC05 CPU core is capable of addressing a 64-Kbyte memory map.
For this implementation, however, the addressing registers are limited to
an 16-Kbyte memory map.
General Release Specification
MC68HC05RC16 — Rev. 3.0
Central Processor Unit
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