D17133CS datasheet(217/289 Pages) NEC

217 / 289 page

CHAPTER 18

INSTRUCTION SET

202

MOV

MEM000, #00H

; Writes 0 to data memory indicated by index register

CLR1

IXE

; IXE flag

← 0

INC

SET2

CMP, Z

; CMP flag

← 1, Z flag ← 1

SUB

IXL, #03H

; Checks whether index register contents

SUBC

IXM, #07H

; are 73H in bank 0

SUBC

IXH, #00H

;

SKT1

; Loops until contents of index register becomes

RAM clear

; 73H of bank 0

18.5.2 Subtraction Instructions

(1)

SUB r, m

Subtract data memory from general register

<1> OP code

00001

<2> Function

When CMP=0, (r)

← (r) – (m)

Subtracts the data memory contents from the general register contents, and stores the result in general

When CMP=1, (r) – (m)

The result is not stored in the register. Carry flag CY and zero flag Z are changed, according to the result.

Sets carry flag CY, if a borrow occurs as a result of the subtraction. Resets the carry flag, if no borrow occurs.

If the subtraction result is other than zero, zero flag Z is reset, regardless of compare flag CMP.

If the subtraction result is zero, with the compare flag reset (CMP=0), the zero flag Z is set.

If the subtraction result is zero, with the compare flag set (CMP=1), the zero flag Z is not changed.

Subtraction can be executed in binary 4-bit or BCD. The BCD flag for program status word PSWORD specifies

which kind of subtraction is to be executed.

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