DESCRIPTION OF INSTRUCTIONS

99. SUBB A, Rr (Substract register from accumulator with borrow)

 

 

7

 

 

 

 

 

 

 

0

 

Instruction code

:

1

0

 

0

1

1

r2

r1

r0

Byte 1

Operation

: (A)(A)–((C)+(Rr))

 

 

 

 

 

Number of bytes

: 1

 

 

 

 

 

 

 

 

 

Number of cycles

: 1

 

 

 

 

 

 

 

 

 

Flags

:

C

AC

F0

RS1

RS0

OV

F1

P

(PSW)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Description

 

 

 

 

 

 

 

 

 

 

 

: The carry flag content and the register r contents are

 

 

substracted from the accumulator contents. The result is placed

 

 

in the accumulator, and the flags are updated.

Example SUBB A, R7

 

 

 

 

 

 

 

 

 

 

 

 

 

7

 

 

 

0

 

 

 

 

 

Instruction code

:

1 0

0 1

 

1 1

1 1

Byte 1

 

 

 

Before execution Carry flag

1

Auxiliary carry flag

0

Overflow flag

0

Register 7

0 1 0 1 1 0 0 0

70 Accumulator

1 0 0 0 0 1 0 0

70

After execution Carry flag

0

Auxiliary carry flag

1

Overflow flag

1

Register 7

0 1 0 1 1 0 0 0

70 Accumulator

0 0 1 0 1 0 1 1

70

359

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Sonic Alert msm83c154s, msm80154s, msm85c154hvs user manual Subb A, Rr Substract register from accumulator with borrow, 359