NEC PD17062 Manuale Utente

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In response to a programmed instruction, the ALU performs 4-bit arithmetic or logic processing, bit

discrimination, comparative discrimination, rotation, or transfer.

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.

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.

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.

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.

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.