Zilog EZ80F916 - Manual (Page 138)

eZ80
®
CPU
User Manual
UM007715-0415 CPU Instruction Set
129
DAA
Decimal Adjust Accumulator
Operation
A  Decimal Adjust (A)
Description
This instruction conditionally adjusts the accumulator, A, following addition and subtrac-
tion operations on binary-coded-decimal (BCD) values. For addition (ADD, ADC, INC)
or subtraction (SUB, SBC, DEC, NEG), Table 51 indicates the operation performed by
the DAA instruction.
Condition Bits Affected
Table 51. Operations of the DAA Instruction
Operation
C Before
DAA
Hex
Value in
Upper
Digit

(Bits 7:4)
H Before
DAA
Hex
Value in
Lower
Digit

(Bits 3:0)
Number
Added to
Byte
C After
DAA H After
DAA
ADD
, ADC,
or INC
0 0–9 0 0–9 00 0 0
0 0–8 0 A–F 06 0 1
0 0–9 1 0–3 06 0 0
0 A–F 0 0–9 60 1 0
0 9–F 0 A–F 66 1 1
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,
DEC
, or
NEG
0 0–9 0 0–9 00 0 0
0 0–8 1 6–F FA 0 0
1 7–F 0 0–9 A0 1 0
1 6–F 1 6–F 9A 1 0
S
Set if the msb of the result is 1 after the operation; reset
otherwise.
Z
Set if result is 0; reset otherwise.
H
See Table 51 .