sbb

1. sbb => sub carry

• add ax,bx => ax - bx - carry

assume cs:code,ds:data,ss:stack

data segment
          db 256 dup(0)
data ends

stack segment stack
           db 128 dup(0)
stack ends

code segment

     start:
           mov ax, stack
           mov ss, ax
           mov sp,128

           mov dx,1000
           mov ax,5
           sub ax,6
           sbb dx,0
     ; AX=0005  BX=0000  CX=0199  DX=03E8  SP=0080  BP=0000  SI=0000  DI=0000
     ; DS=0E14  ES=0E14  SS=0E34  CS=0E3C  IP=000E   NV UP EI PL NZ NA PO NC
     ; 0E3C:000E 83E806        SUB     AX,+06
     ; -t

     ; AX=FFFF  BX=0000  CX=0199  DX=03E8  SP=0080  BP=0000  SI=0000  DI=0000
     ; DS=0E14  ES=0E14  SS=0E34  CS=0E3C  IP=0011   NV UP EI NG NZ AC PE CY
     ; 0E3C:0011 83DA00        SBB     DX,+00
     ; -t

     ; AX=FFFF  BX=0000  CX=0199  DX=03E7  SP=0080  BP=0000  SI=0000  DI=0000
     ; DS=0E14  ES=0E14  SS=0E34  CS=0E3C  IP=0014   NV UP EI PL NZ NA PE NC

           mov ax,4C00H
           int 21H

code ends
end start