IA8044/IA8344
Data Sheet
SDLC Communications Controller
March 30, 2010
4.8
General CPU Registers
4.8.1 Accumulator (ACC)
Table 22 presents the Accumulator Register. Most instructions use the accumulator to hold the
operand. The mnemonics for accumulator-specific instructions refer to accumulator as A, not
ACC.
Table 22. Accumulator Register
7
6
5
4
3
2
1
0
ACC.7 ACC.6 ACC.5 ACC.4 ACC.3 ACC.2 ACC.1 ACC.0
4.8.2 B Register (B)
Table 23 presents the B register, which is used during multiply and divide instructions. It can also
be used as a scratch-pad register to hold temporary data.
Table 23. B Register
7
6
5
4
3
2
1
0
B.7 B.6 B.5 B.4 B.3 B.2 B.1 B.0
4.8.3 Program Status Word (PSW)
Table 24 presents program status word, which contains CPU status flags, register select bits, and
user flags.
Table 24. Program Status Word Register
7
6
5
4
3
2
1
0
CY AC F0 RS1 RS0 OV
–
P
Bit [7]—CY → (PSW.7) Carry flag for carry out of or into Bit [7]
Bit [6]—AC → (PSW.7) Auxiliary carry flag for carry out of or into Bit [3]
Bit [5]—F0 → (PSW.7) General purpose Flag 0 available for user
Bit [4]—RS1 → (PSW.7) Register bank select control Bit [1], used to select working
register bank
Bit [3]—RS0 → (PSW.7) Register bank select control Bit [0], used to select working
register bank
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