Zilog Z80380 Instrukcja Użytkownika Pobierz pdf (Strona 76)

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Z380

™

USER'S MANUAL

DC-8297-03

ZILOG

DAA

DECIMAL ADJUST ACCUMULATOR

DAA

Operation: A ← Decimal Adjust A

The accumulator is adjusted to form two 4-bit BCD digits following a binary, two’s

complement addition or subtraction on two BCD-encoded bytes. The table below indicates

the operation performed for addition (ADD, ADC, INC) or subtraction (SUB, SBC, DEC,

NEG).

C Hex Value H Hex Value Number C H

Before Upper Digit Before Lower Digit Added After After

Operation DAA (Bits 7-4) DAA (Bits 3-0) to Byte DAA DAA

0 0-9 0 0-9 00 0 0

0 0-8 0 A-F 06 0 1

ADD 0 0-9 1 0-3 06 0 0

ADC 0 A-F 0 0-9 60 1 0

INC 0 9-F 0 A-F 66 1 1

(N=0) 0 A-F 1 0-3 66 1 0

1 0-2 0 0-9 60 1 0

1 0-2 0 A-F 66 1 1

1 0-3 1 0-3 66 1 0

SUB

SBC 0 0-9 0 0-9 00 0 0

DEC 0 0-8 1 6-F FA 0 1

NEG 1 7-F 0 0-9 A0 1 0

(N=1) 1 6-F 1 6-F 9A 1 1

Flags: S: Set if the most significant bit of the result is set; cleared otherwise

Z: Set if the result is zero; cleared otherwise

H: See table above

P: Set if the parity of the result is even; cleared otherwise

N: Not affected

C: See table above

Addressing Execute

Mode Syntax Instruction Format Time Note

DAA 00100111 3

1 2 ... 71 72 73 74 75 76 77 78 79 80 81 ... 267 268

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