MC68HC05P4A Datasheet, PDF (22/72 Pages) Advanced Analogic Technologies – Microcontrollers

Central Processor Unit (CPU)
3.4.4 Z — Zero
When set, this bit indicates that the result of the last arithmetic, logical, or data manipulation was 0.
3.4.5 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.
3.5 Stack Pointer (SP)
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 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 (MSB) are permanently set to 0000011. These
seven bits are appended to the six least significant bits (LSB) 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.
12
7
0
0
0
0
0
1
1
0
SP
3.6 Program Counter (PC)
The program counter is a 13-bit register that contains the address of the next byte to be fetched.
12
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
8-Kbyte memory map.
MC68HC05P4A Data Sheet, Rev. 7.1
22
Freescale Semiconductor