NEC PD17062 - Manual (Page 49)

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PD17062
7.2 CONFIGURATION AND FUNCTIONS OF THE COMPONENTS OF THE ALU BLOCK
7.2.1 ALU
In response to a programmed instruction, the ALU performs 4-bit arithmetic or logic processing, bit
discrimination, comparative discrimination, rotation, or transfer.
7.2.2 Temporary Storage Registers A and B
Temporary storage registers A and B temporarily hold the 4-bit data.
These registers are automatically used when an instruction is executed. They cannot be controlled by a
program.
7.2.3 Program Status Word
A program status word controls the operation of the ALU and holds the status of the ALU.
For details of the program status word, see Section 8.7.
7.2.4 Decimal Conversion Circuit
If the BCD flag of the program status word is set to 1 when an arithmetic operation is executed, the decimal
conversion circuit converts the results of the arithmetic operation to a decimal number.
7.2.5 Address Controller
The address controller specifies an address in data memory.
At the same time, the circuit also controls address modification by the index register or data memory row
address pointer.
7.3 ALU OPERATIONS
Table 7-1 lists the operations performed by the ALU when instructions are executed.
Table 7-2 shows the data memory address modification by the index register and data memory row address
pointer.
Table 7-3 lists the converted decimal data used in decimal operations.