mc68hc705j2 Freescale Semiconductor, Inc, mc68hc705j2 Datasheet - Page 21

• Manufacturer Part Number: mc68hc705j2
• Description: 8-bit Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

4.1.1 Accumulator
4.1.2 Index Register
4.1.3 Stack Pointer
MOTOROLA
4-2
The accumulator is a general-purpose 8-bit register.
accumulator to hold operands and results of arithmetic and nonarithmetic
operations.
The 8-bit index register can perform two functions:
In indexed addressing, the CPU uses the byte in the index register to determine
the conditional address of the operand.
4.3.6 Indexed, 8-Bit Offset, and 4.3.7 Indexed, 16-Bit Offset.
The index register can also serve as an auxiliary accumulator for temporary
storage.
The stack pointer is a 16-bit register that contains the address of the next free
location on the stack. During a reset or after the reset stack pointer (RSP)
instruction, the stack pointer contents are preset to $00FF. The address in the
stack pointer decrements as data is pushed onto the stack and increments as
data is pulled from the stack.
The ten most significant bits of the stack pointer are permanently fixed at
0000000011, so the stack pointer produces addresses from $00C0 to $00FF. If
subroutines and interrupts use more than 64 stack locations, the stack pointer
wraps around to address $00C0 and begins writing over the previously stored
data. A subroutine uses two stack locations; an interrupt uses five locations.
• Indexed addressing
• Temporary storage
CENTRAL PROCESSOR UNIT
See 4.3.5 Indexed, No Offset,
The CPU uses the
MC68HC705J2