djnz r7,loop20ret;xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx;
cac chuong trinh con ;xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxthuan09: mov a,r0rr amov r0,aclr cmov a,r3rrc amov r3,aretxnguoc09: mov a,20hclr crlc amov 20h,aret;xxxxx[r]