MC9S12T64 Datasheet, PDF (27/608 Pages) Motorola, Inc – Specification

Freescale Semiconductor, Inc.
Central Processing Unit (CPU)
Programming Model
7
6
5
4
3
2
1
0
Read:
Write:
Reset: 0
0
0
0
0
0
0
0
Figure 3 Accumulator A
7
6
5
4
3
2
1
0
Read:
Write:
Reset: 0
0
0
0
0
0
0
0
Figure 4 Accumulator B
Most operations can use accumulator A or B interchangeably. However,
there are a few exceptions. Add, subtract, and compare instructions
involving both A and B (ABA, SBA, and CBA) only operate in one
direction, so it is important to verify that the correct operand is in the
correct accumulator. The decimal adjust accumulator A (DAA)
instruction is used after binary-coded decimal (BCD) arithmetic
operations. There is no equivalent instruction to adjust accumulator B.
Index Registers (X
and Y)
16-bit index registers X and Y are used for indexed addressing. In
indexed addressing, the contents of an index register are added to a
5-bit, 9-bit, or 16-bit constant or to the contents of an accumulator to form
the effective address of the instruction operand. Having two index
registers is especially useful for moves and in cases where operands
from two separate tables are used in a calculation.
Central Processing Unit (CPU)
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MC9S12T64Revision 1.1.1