Datasheet

Central Processor Unit (CPU12)
MC68HC812A4 Data Sheet, Rev. 7
44 Freescale Semiconductor
3.3 CPU Registers
This section describes the CPU registers.
3.3.1 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.
3.3.2 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 7654321Bit 0
A7 A6 A5 A4 A3 A2 A1 A0
Reset: Unaffected by reset
Figure 3-2. Accumulator A (A)
Bit 7654321Bit 0
B7 B6 B5 B4 B3 B2 B1 B0
Reset: Unaffected by reset
Figure 3-3. Accumulator B (B)
Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 Bit 0
D15
(A7)
D14
(A6)
D13
(A5)
D12
(A4)
D11
(A3)
D10
(A2)
D9 (A1) D8 (A0) D7 (B7) D6 (B6) D5 (B5) D4 (B4) D3 (B3) D2 (B2) D1 (B1) D0 (B0)
Reset: Unaffected by reset
Figure 3-4. Accumulator D (D)