MC912DG128A Motorola, MC912DG128A Datasheet - Page 22

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

Programming Model
Central Processing Unit
MC68HC912DT128A Rev 2.0
22
CPU12 registers are an integral part of the CPU and are not addressed
as if they were memory locations.
Accumulators A and B are general-purpose 8-bit accumulators used to
hold operands and results of arithmetic calculations or data
manipulations. Some instructions treat the combination of these two
8-bit accumulators as a 16-bit double accumulator (accumulator D).
Index registers X and Y are used for indexed addressing mode. In the
indexed addressing mode, the contents of a 16-bit index register are
added to 5-bit, 9-bit, or 16-bit constants or the content of an accumulator
to form the effective address of the operand to be used in the instruction.
15
15
15
15
15
7
A
Central Processing Unit
Figure 3 Programming Model
0
PC
SP
IX
IY
D
7
S X H I
B
N
Z V C
0
0
0
0
0
0
8-BIT ACCUMULATORS A & B
OR
16-BIT DOUBLE ACCUMULATOR D
INDEX REGISTER X
INDEX REGISTER Y
STACK POINTER
PROGRAM COUNTER
CONDITION CODE REGISTER
MOTOROLA
2--cpu12