NEC 78K/0S Series User Manual page 80

DEC
[Instruction format]
[Operation]
[Operand]
Mnemonic
DEC r
saddr
[Flag]
Z AC
× ×
[Description]
•
The destination operand (dst) contents are decremented by only one.
•
If the decrement result is 0, the Z flag is set (1). In all other cases, the Z flag is cleared (0).
•
If the decrement generates a carry from bit 4 to bit 3, the AC flag is set (1). In all other cases, the AC flag is
cleared (0).
•
Because this instruction is frequently used for a counter for repeated operations, the CY flag contents are
not changed (to hold the CY flag contents in multiple-byte operation).
•
If dst is the B or C register or saddr, and it is not desired to change the AC and CY flag contents, the DBNZ
instruction can be used.
[Description example]
DEC 0FE92H ; The contents at address FE92H are decremented.
80
CHAPTER 5 EXPLANATION OF INSTRUCTIONS
DEC dst
dst ← dst – 1
Operand (dst)
CY
User's Manual U11047EJ3V0UM00
Decrement
Byte Data Decrement