anl a,#0fh ;xoa 4 bit cao hang chuc giomovc a,@a+dptr;lay ma 7 doanmov 23h,a ;cat ma vao o nho 23hmov a,gioanl a,#0f0h ;xoa 4 bit thap hang dvi gioswap a ;chuyen 4 bit cao xuong vi tri thapmovc a,@a+dptr;lay ma 7 doan hang chucmov 22h,a ;cat vao o nho 22hret;xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx[r]