单片机应用技术教案双语教学4Ch4 The Program Design of Assembly Language.docVIP

Ch4???The?Program?Design?of?Assembly?Language Keywords： Introduction：’ll tell you how to design a program. To gain the full depth contained in each lines explanation, we highly recommend you refer to each line and its description. Line1: stack This defines the stack entry point, all win32 programs contain a STACK. Line2: data All data definitions are defined here Line3: code All Program code to be executed goes below this statement Line4: START: This line tells the compiler where to execute the MAIN code. All code within the START and END START labels is executed. The program will LOOP through the contents until END START is found. Anything with a proceeding : is a label. Line5: mov AX, seg msg We call upon the asm mov instruction to mov the contents of segment of msg into the AX Register. Mov is as follows: mov destination, source Eg: mov AX, 10 would place the value 10 into the AX register. Line6: mov ds, AX Because we cannot move immediate data directly into the DS and ES registers, we must move our data into the general purpose registers, and then from there, into the Data Segment and Extra Segments. Line7: END START What I have left out above are the lines that contain ;s A line that contains a ; carries a comment. Anything after the ; is considered to be a comment, and is ignored by the compiler. A comment helps improve program readability. Hopefully this small example program will help you on your way to learning the basics to assembler programming. To help you on your journey, I will now give you some fun interrupts to play with, that may help you discover new and exciting things =) Interrupts One interrupt in which is found rather handy is 16H, which waits for a single keypress from the keyboard, the following code will pause the program until a key has been pressed: Nearly all interrupts will call upon the registers as variables when they execute their instructions. For interrupt 16h , we must clear the ax register. Interrupt 1