ZiLOG eZ80 User Manual page 138

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),
the DAA instruction.
Table 51. Operations of the DAA Instruction
Operation
ADD, ADC,
or INC
SUB, SBC,
DEC, or
NEG
Condition Bits Affected
S
Z
H
UM007714-0908
Hex
Value in
Upper
C Before Digit
DAA (Bits 7:4)
0 0–9
0 0–8
0 0–9
0 A–F
0 9–F
0 A–F
1 0–2
1 0–2
1 0–3
0 0–9
0 0–8
1 7–F
1 6–F
Set if the msb of the result is 1 after the operation; reset
otherwise.
Set if result is 0; reset otherwise.
See .
Table 51
Table 51 indicates the operation performed by
Hex
Value in
Lower Number
H Before Digit Added to
DAA (Bits 3:0) Byte
0 0–9 00
0 A–F 06
1 0–3 06
0 0–9 60
0 A–F 66
1 0–3 66
0 0–9 60
0 A–F 66
1 0–3 66
0 0–9 00
1 6–F FA
0 0–9 A0
1 6–F 9A
®
eZ80 CPU
User Manual
C After H After
DAA DAA
0 0
0 1
0 0
1 0
1 1
1 0
1 0
1 1
1 0
0 0
0 0
1 0
1 0
CPU Instruction Set
129