What are the values in SI,DI,CX, and DF (Direction Flag)? 5. Start emulation by clicking the emulate button on the toolbar. What is the equivalent instructions for LODSB and SCASB? Hint: you can use the Complete 8086 instruction set tutorial from (help->emu8086 reference-> Complete 8086 instruction set),or from the help folder at the source directory of the emulator,to know how the instructions are executed and what are the flags affected by these instructions. Using the assembler editor, enter the following codes: #make_com# COM file is loaded at CS:0100h ORG 100h CLD LEA SI, str1 LEA DI, str2 MOV CX, 8 L2: LODSB SCASB JNZ L1 LOOP L2 MOV DL, 'Y' JMP 元 L1: MOV DL, 'N' 元: HLT str1 DB 4, A, 6, 6, 2, 6, 0, 5, 8 str2 DB 4, A, 6, 6, 2, 1, 0, 9, 8 Q3.
#EMU8086 CODE CODE#
To re-execute the program click on the Reload icon or write the first IP address in the program which is here IP=0100 in the IP field then click on Run icon.Ĥ Code example 2 1. To run the whole program (not step by step), click the Run icon, and then you can see the final result of your program. Repeat step 4 until the end of the program. Hint: to show the contents of flags by pressing the FLAGS button.
Record the values of IP, AL, BL, and the flags (CF,AF,ZF). Single-step the program codes by pressing the single step button. What are the values of CS,DS,SP, and IP? 4. In memory list first row is an offset, second row is a hexadecimal value, third row is decimal value, and last row is an ASCII character value.
#EMU8086 CODE FULL#
The offset of var1 is 010Ch, and full address is 0B56:010C. By default segment is loaded in DS register (when COM files is loaded the value of DS register is set to the same value as CS register - code segment). When compiler makes machine code, it automatically replaces all variable names with their offsets. As you see this looks a lot like our example, except that variables are replaced with actual memory locations. You can see your code in the most right yellow column and the machine code of the program in the next yellow column. You can also see the Arithmetic and Logic Unit (ALU) inputs and output. A new emulator window will appear.ģ You can see in it the general registers file (AX, BX ), instruction pointer (IP), segment register file (CS, DS ), flags, stack, and memory locations. After writing the previous program, it should appear like the following:Ģ 3. Using the assembler editor, enter the following codes: %%%%%% #make_com# COM file is loaded at CS:0100h ORG 100h MOV AL, B AL=8C MOV BL,var1 BL=5 ADD AL,BL AL=AL+BL=91 & AF=1(AUXULARY FLAG) ADD BL,0FBH BL=BL+FB=00 & AF=1,CF=1,ZF=1 HLT stop here var1 DB 5 %%%%%% The symbol ( ) acts like (//) in C++, writing a comment. Example on the emulator to see how it works Open the emulator (ALL programs -> Emu8086 version 3.04-> Emu8086 version 3.04), press continue. Another advantage in this emulator, the program can be executed step by step to get the error position or can be executed altogether. The program has the capability to show the conditions of the general registers file (AX, BX ), instruction pointer (IP), segment register file (CS, DS ), flags, stack, and memory locations, which simplify assuring the steps of the program. Actually we can generate an EXE file from the emulator and run itt. Our emulator (Emu8086) has the advantage of writing with assembly language directly and converting to machine language automatically to write it through the keyboard into the kit. If after running the program there are more unsatisfied results you should review and fix your code again until you reach your goal. In the first case you should review your code and fix the error then you will reconvert the fixed code in both cases.
If you are not satisfied with the results, there may be an error in your program, which is most probably, or in the format converting. You should first write the program in assembly then according to the 8086 instruction set formats convert from assembly to machine code then enter the program through the keyboard on the kit then run your program. 1 Emulator (Emu8086) Overview Imagine we want to run a program on the MDA-8086 microprocessor training kit.
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