NEC 78K/0 Series - Manual (Page 58)

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CHAPTER 5 EXPLANATION OF INSTRUCTIONS
User's Manual U12326EJ4V0UM
Subtract with Carry
SUBC
Subtraction of Byte Data with Carry
[Instruction format] SUBC dst, src
[Operation] dst, CY
← dst – src – CY
[Operand]
Mnemonic Operand(dst,src) Mnemonic Operand(dst,src)
SUBC A, #byte SUBC A, !addr16
saddr, #byte A, [HL]
A, r Note A, [HL+byte]
r, A A, [HL+B]
A, saddr A, [HL+C]
Note Except r = A
[Flag]
Z AC CY
Ч Ч Ч
[Description]
• The source operand (src) specified by the 2nd operand and the CY flag are subtracted from the destination
operand (dst) specified by the 1st operand and the result is stored in the destination operand (dst).
The CY flag is subtracted from the least significant bit. This instruction is mainly used for subtraction of two
or more bytes.
• If the subtraction shows that dst is 0, the Z flag is set (1). In all other cases, the Z flag is cleared (0).
• If the subtraction generates a borrow out of bit 7, the CY flag is set (1). In all other cases, the CY flag is
cleared (0).
• If the subtraction generates a borrow for bit 3 out of bit 4, the AC flag is set (1). In all other cases, the AC
flag is cleared (0).
[Description example]
SUBC A, [HL]; The (HL register) address contents and the CY flag are subtracted from the A register and
the result is stored in the A register.