NEC 78K/0 Series User Manual page 72

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 for bit 3 out of bit 4, the AC flag is set (1). In all other cases, the AC
flag is cleared (0).
• Because this instruction is frequently used for decrement of a counter for repeated operations and an indexed
addressing offset register, 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 FE92H; The contents at address FE92H are decremented.
72
CHAPTER 5 EXPLANATION OF INSTRUCTIONS
DEC dst
dst ← dst – 1
Operand(dst)
CY
User's Manual U12326EJ4V0UM
Decrement
Byte Data Decrement