KS57C2308/P2308/C2316/P2316

SAM47 INSTRUCTION SET

 

 

SBC — Subtract With Carry

SBC(Continued)

Examples: 3. If SBC A,@HL is followed by an ADS A,#im, the SBC skips on “no borrow” to the instruction immediately after the ADS. An “ADSA,#im” instruction immediately after the “SBC A,@HL” instruction does not skip even if an overflow occurs. This function is useful for decimal adjustment operations.

a. 8 – 6 decimal addition (the contents of the address specified by the HL register is 6H):

RCF

 

;

C "0"

LD

A,#8H

;

A

8H

SBC

A,@HL

;

A

8H – 6H – C(0) = 2H, C "0"

ADS

A,#0AH

;

Skip this instruction because no borrow after SBC result

JPS

XXX

 

 

 

 

b. 3 – 4 decimal addition (the contents of the address specified by the HL register is 4H):

RCF

 

;

C "0"

LD

A,#3H

;

A 3H

SBC

A,@HL

;

A 3H – 4H – C(0) = 0FH, C "1"

ADS

A,#0AH

;

No skip. A 0FH + 0AH = 9H

 

 

; (The skip function of “ADSA,#im” is inhibited after a

 

 

; “SBC A,@HL” instruction even if an overflow occurs.)

JPS

XXX

 

 

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Samsung KS57C2308 manual #8H