MC912DG128A Motorola, MC912DG128A Datasheet - Page 23

• Manufacturer Part Number: MC912DG128A
• Description: Microcontrollers
• Manufacturer: Motorola

Data Types
3-cpu12
MOTOROLA
Stack pointer (SP) points to the last stack location used. The CPU12
supports an automatic program stack that is used to save system
context during subroutine calls and interrupts, and can also be used for
temporary storage of data. The stack pointer can also be used in all
indexed addressing modes.
Program counter is a 16-bit register that holds the address of the next
instruction to be executed. The program counter can be used in all
indexed addressing modes except autoincrement/decrement.
Condition Code Register (CCR) contains five status indicators, two
interrupt masking bits, and a STOP disable bit. The five flags are half
carry (H), negative (N), zero (Z), overflow (V), and carry/borrow (C). The
half-carry flag is used only for BCD arithmetic operations. The N, Z, V,
and C status bits allow for branching based on the results of a previous
operation.
The CPU12 supports the following data types:
A byte is eight bits wide and can be accessed at any byte location. A
word is composed of two consecutive bytes with the most significant
byte at the lower value address. There are no special requirements for
alignment of instructions or operands.
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Bit data
8-bit and 16-bit signed and unsigned integers
16-bit unsigned fractions
16-bit addresses
Central Processing Unit
MC68HC912DT128A Rev 2.0
Central Processing Unit
Data Types
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