Adjba – NEC 78K/0 Series User Manual
Page 83
CHAPTER 5 EXPLANATION OF INSTRUCTIONS
83
User's Manual U12326EJ4V0UM
Decimal Adjust Register for Addition
ADJBA
Decimal Adjustment of Addition Result
[Instruction format]
ADJBA
[Operation]
Decimal Adjust Accumulator for Addition
[Operand]
None
[Flag]
Z
AC
CY
Ч
Ч
Ч
[Description]
•
The A register, CY flag and AC flag are decimally adjusted from their contents. This instruction carries out
an operation having meaning only when the BCD (binary coded decimal) data is added and the addition result
is stored in the A register (in all other cases, the instruction carries out an operation having no meaning).
See the table below for the adjustment method.
•
If the adjustment result shows that the A register contents are 0, the Z flag is set (1). In all other cases,
the Z flag is cleared (0).
Condition
Operation
A
3
to A
0
≤ 9
A
7
to A
4
≤ 9 and CY = 0
A
← A, CY ← 0, AC ← 0
AC = 0
A
7
to A
4
≥ 10 or CY = 1
A
← A+01100000B, CY ← 1, AC ← 0
A
3
to A
0
≥ 10
A
7
to A
4
< 9 and CY = 0
A
← A+00000110B, CY ← 0, AC ← 1
AC = 0
A
7
to A
4
≥ 9 or CY = 1
A
← A+01100110B, CY ← 1, AC ← 1
AC = 1
A
7
to A
4
≤ 9 and CY = 0
A
← A+00000110B, CY ← 0, AC ← 0
A
7
to A
4
≥ 10 or CY = 1
A
← A+01100110B, CY ← 1, AC ← 0