What is SUBB instruction in 8051 microcontroller? All Questions › Category: Embedded System › What is SUBB instruction in 8051 microcontroller? 0 Vote Up Vote Down Chetan Shidling Staff asked 5 years ago I need short information. 1 Answers -1 Vote Up Vote Down Chetan Shidling Staff answered 5 years ago Its function is to subtract with the barrow. Subtract the source-byte and the carry flag from the accumulator and set the result in the accumulator. Example: MOV A, #45H CLR C SUBB A, #22H