Sonic Alert msm85c154hvs Arithmetic Operation Section, PSW0D0H CY AC F0 RS1 RS0 OV F1 P

SYSTEM CONFIGURATION

2.8 Arithmetic Operation Section

(1)Outline

The MSM80C154S/MSM83C154S arithmetic operation section consists of

(1)an arithmetic operation instruction decoder, and

(2)an arithmetic and logic unit [ALU].

(2)Arithmetic operation instruction decoder:

Arithmetic operation instructions are passed to the instruction register (IR) and then to the PLA where they are converted into control signals.

The control signals from the PLA are used to control ALU peripheral circuits and ALU arithmetic operations (ADD, AND, OR, EOR).

(3)Arithmetic and logic unit [ALU]:

Upon reception of 8-bit data from one or two data sources the ALU processes that data in accordance with control signals from the PLA. The ALU is capable of executing the following processes:

• Additions and subtractions with and without carry

• Increments (+1) and decrements (–1)

• Bit complements

• Rotations (either direction with and without carry)

• BCD (decimal adjust)

• Carry, auxiliary carry, and overflow signal output

• Multiplications and divisions

• Bit detection

• Exchange of low and high order nibbles

• Logical AND, logical OR, and exclusive OR

If a bit-3 auxiliary carry (AC), a bit-7 carry (CY), or an overflow (OV) is generated as a result of the arithmetic operation executed by the ALU, that result is set in the program status word (PSW 0D0H).

PSW(0D0H)

CY AC F0 RS1 RS0 OV F1 P

7 6 5 4 3 2 1 0

Figure 2-22 Program status word

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