MC68HC812A4 Datasheet, PDF (61/342 Pages) Motorola, Inc – 16-bit device composed of standard on-chip peripheral modules connected by an intermodule bus. Modules include

Central Processor Unit (CPU12)
CPU Registers
3.4.1 Accumulators A and B
Accumulators A and B are general-purpose 8-bit accumulators that
contain operands and results of arithmetic calculations or data
manipulations.
Bit 7
A7
Reset:
6
5
4
3
2
A6
A5
A4
A3
A2
Unaffected by reset
Figure 3-2. Accumulator A (A)
1
Bit 0
A1
A0
Bit 7
B7
Reset:
6
5
4
3
2
B6
B5
B4
B3
B2
Unaffected by reset
Figure 3-3. Accumulator B (B)
1
Bit 0
B1
B0
3.4.2 Accumulator D
Accumulator D is the concatenation of accumulators A and B. Some
instructions treat the combination of these two 8-bit accumulators as a
16-bit double accumulator.
Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 Bit 0
D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
(A7) (A6) (A5) (A4) (A3) (A2) (A1) (A0) (B7) (B6) (B5) (B4) (B3) (B2) (B1) (B0)
Reset:
Unaffected by reset
Figure 3-4. Accumulator D (D)
Advance Information
MOTOROLA
Central Processor Unit (CPU12)
MC68HC812A4 — Rev. 3.0
61