Microsoft PowerPoint - C15_LECTURE_NOTE_04.ppt

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1 MACHINE LANGUAGE CODING AND THE DEBUG SOFTWARE DEVELOPMENT PROGRAM OF THE PC MACHINE LANGUAGE CODING AND THE DEBUG SOFTWARE DEVELOPMENT PROGRAM OF THE PC 4.1 Converting Assembly Language Instructions to Machine Code 4.2 Encoding a Complete Program in Machine Code 4.3 The PC and Its DEBUG Program 4.4 Examining and Modifying the Contents of Memory 4.5 Input and Output of Data 微處理機原理與應用 Lecture

2 THE DEBUG, A SOFTWARE DEVELOPMENT PROGRAM FOR THE PC 4.6 Hexadecimal Addition and Subtraction 4.7 Loading, Verifying and Saving Machine Language Program 4.8 Assembling Instructions with the Assemble Command 4.9 Executing Instructions and Programs with the TRACE and GO command 4.10 Debugging a Program 微處理機原理與應用 Lecture Converting Assembly Language Instructions to Machine Code General instruction format for machine code 微處理機原理與應用 Lecture

3 4.1 Converting Assembly Language Instructions to Machine Code Byte 1 specification Opcode field (6-bits) Specifies the operation to be performed Register direction bit (D-bit) 1 the register operand is a destination operand 0 the register operand is a source operand Data size bit (W-bit) 1 16-bit data size 0 8-bit data size 微處理機原理與應用 Lecture Converting Assembly Language Instructions to Machine Code Byte 2 specification Mode (MOD) field (2-bits) Together with R/M field to specify the second operand Register (REG) field (3-bit) Identifies the register for the first operand Register/Memory (R/M) field (3-bit) Register (REG) field encoding 微處理機原理與應用 Lecture

4 4.1 Converting Assembly Language Instructions to Machine Code Byte 2 specification MOD field and R/M field encoding 微處理機原理與應用 Lecture Converting Assembly Language Instructions to Machine Code MOV BL, AL Encode the above instruction in machine code OPCODE = (for MOV), D = 0 (source), W = 0 (8-bit) This leads to BYTE 1 = = In byte 2 the source operand, specified by REG, is AL REG = 000, MOD = 11, R/M = 011 Therefore, BYTE 2 = = C3 16 MOV BL, AL = 88C 微處理機原理與應用 Lecture

5 4.1 Converting Assembly Language Instructions to Machine Code ADD AX, [SI] Encode the above instruction in machine code OPCODE = (for ADD), D = 1 (dest.), W = 1 (16-bit) This leads to BYTE 1 = = In byte 2 the destination operand, specified by REG, is AX REG = 000, MOD = 00, R/M = 100 Therefore, BYTE 2 = = ADD AX, [SI] = 微處理機原理與應用 Lecture Converting Assembly Language Instructions to Machine Code XOR CL, [1234H] Encode the above instruction in machine code OPCODE = (for XOR), D = 1 (dest.), W = 0 (8-bit) This leads to BYTE 1 = = In byte 2 the destination operand, specified by REG, is CL REG = 001, MOD = 00, R/M = 110 Therefore, BYTE 2 = = 0E 16 BYTE 3 = BYTE 4 = XOR CL, [1234H] = 320E 微處理機原理與應用 Lecture

6 4.1 Converting Assembly Language Instructions to Machine Code ADD [BX][DI]+1234H, AX Encode the above instruction in machine code OPCODE = (for ADD), D = 0 (source), W = 1 (16-bit) This leads to BYTE 1 = = In byte 2 the destination operand, specified by REG, is AX REG = 000, MOD = 10, R/M = 001 Therefore, BYTE 2 = = BYTE 3 = BYTE 4 = ADD [BX][DI]+1234H, AX = 微處理機原理與應用 Lecture Converting Assembly Language Instructions to Machine Code Additional one-bit field and their functions Field S V Z Value Function No sign extension Sign extend 8-bit immediate data to 16 bits if W=1 Shift/rotate count is one Shift/rotate count is specified in CL register Repeat/loop while zero flag is clear Repeat/loop while zero flag is set Instructions that involve a segment register (SR-field) Register ES CS SS DS 微處理機原理與應用 Lecture SR

7 4.1 Converting Assembly Language Instructions to Machine Code MOV WORD PTR [BP][DI]+1234H, 0ABCDH Encode the above instruction in machine code This example does not follow the general format From Fig. 3-1 MOV -> W, and W = 1 for word-size data BYTE 1 = = C7 16 BYTE 2 = (MOD)000(R/M) = = BYTE 3 = BYTE 4 = BYTE 5 = CD 16 BYTE 6 = AB 16 MOV WORD PTR [BP][DI]+1234H, 0ABCDH = C CDAB 微處理機原理與應用 Lecture Converting Assembly Language Instructions to Machine Code MOV [BP][DI]+1234H, DS Encode the above instruction in machine code This example does not follow the general format From Fig. 3-6 MOV -> , and the instruction is (MOD)0(SR)(R/M)(DISP) From Fig. 4-5 we find that for DS, the SR = 11 Therefore, the instruction is coded as MOV [BP][DI]+1234H, DS = =8C9B 微處理機原理與應用 Lecture

8 4.2 Encoding a Complete Program in Machine Code Steps in encoding a complete assembly program: Identify the general machine code format (Fig. 3-6) Evaluate the bit fields (Fig. 4-2,4-3,4-4,4-5) Express the binary-code instruction in hexadecimal form To execute the program, the machine code of the program must be stored in the code segment of memory. The first byte of the program is stored at the lowest address 微處理機原理與應用 Lecture Encoding a Complete Program in Machine Code Encode the block move program in Fig. 4-6(a) and show how it would be stored in memory starting at address MOV AX, 2000H MOV DS, AX MOV SI, 100H MOV DI, 120H MOV CX, 10H NXTPT: MOV AH, [SI] MOV [DI], AH INC SI INC DI DEC CX JNZ NXTPT NOP ;LOAD AX REGISTER ;LOAD DATA SEGMENT ADDRESS ;LOAD SOURCE BLOCK POINTER ;LOAD DESTINATION BLOCK POINTER ;LOAD REPEAT COUNTER ;MOVE SOURCE BLOCK ELEMENT TO AH ;MOVE ELEMENT FROM AH TO DEST. BLOCK ;INCREMENT SOURCE BLOCK POINTER ;INCREMENT DESTINATION BLOCK POINTER ;DECREMENT REPEAT COUNTER ;JUMP TO NXTPT IF CX NOT EQUAL TO ZERO ;NO OPERATION 微處理機原理與應用 Lecture

9 4.2 Encoding a Complete Program in Machine Code 微處理機原理與應用 Lecture Encoding a Complete Program in Machine Code 微處理機原理與應用 Lecture

10 4.3 The PC and Its DEBUG Program Using DEBUG, the programmer can issue commands to the microcomputer. Loading the DEBUG program C:\DEBUG Six kinds of information are entered as part of a command: A command letter An address A register name A file name A drive name Data 微處理機原理與應用 Lecture The PC and Its DEBUG Program The DEBUG program command set 微處理機原理與應用 Lecture

11 4.3 The PC and Its DEBUG Program An initial state when with the loading of DEBUG 0100 IP Memory 1342 CS 1342 DS 1342 SS 1342 ES 0000 AX 0000 BX 0000 CX 0000 DX Active code segment, data segment, stack segment, and extra segment (64 K bytes) FFEE SP 0000 BP 0000 SI 0000 DI 0040 Flags FFFFF 8088/8086 MPU 微處理機原理與應用 Lecture The PC and Its DEBUG Program Syntax for the REGISTER (R) command R [REGISTER NAME] e.g. -R AX ( ) AX 0000 :_ :00FF ( ) _ ;This alter the content of AX 微處理機原理與應用 Lecture

12 4.3 The PC and Its DEBUG Program Verify the initialized state of the 8088 by examining the contents of its registers with the Register command -R ( ) 微處理機原理與應用 Lecture The PC and Its DEBUG Program Register mnemonics for the R command Symbol AX BX CX DX SI DI SP BP CS DS SS ES F IP Register Accumulator register Base register Count register Data register Source index register Destination index register Stack pointer register Base pointer register Code segment register Data segment register Stack segment register Extra segment register Flag register Instruction pointer 微處理機原理與應用 Lecture

13 4.3 The PC and Its DEBUG Program Status flag notations Flag Meaning Set Reset OF Overflow OV NV DF Direction DN UP IF Interrupt EI DI SF Sign NG PL ZF Zero ZR NZ AF Auxiliary carry AC NA PF Parity PE PO CF Carry CY NC 微處理機原理與應用 Lecture The PC and Its DEBUG Program Issue commands to the DEBUG program on the PC that causes the value in BX to be modified to FF00 16 and then verify that this new value is loaded into BX. -R BX ( ) BX 0000 :FF00 ( ) -R BX ( ) BX FF00 :_ ( ) _ 微處理機原理與應用 Lecture

14 4.3 The PC and Its DEBUG Program Use the Register command to set the parity flag to even parity. Verify that the flag has been changed. -R F ( ) NV UP EI PL NZ NA PO NC -PE ( ) -R F ( ) NV UP EI PL NZ NA PE NC - ( ) 微處理機原理與應用 Lecture Examining and Modifying the Contents of Memory The commands provided for use in examining and modifying the memory: DUMP ENTER FILL MOVE COMPARE SERACH 微處理機原理與應用 Lecture

15 4.4 Examining and Modifying the Contents of Memory DUMP Command (D) The DUMP command allows us to examine the contents of a memory location or a block of consecutive memory location. D [ADDRESS] e.g. -D ( ) -D 1342:100 ( ) -D DS:100 ( ) -D 100 ( ) 微處理機原理與應用 Lecture Examining and Modifying the Contents of Memory DUMP Command (D) Address of the first byte of data ASCII version of the memory data 微處理機原理與應用 Lecture bytes of data per line, 128 bytes per dump 15

16 4.4 Examining and Modifying the Contents of Memory Issue a dump command to display the contents of the 32 bytes of memory located at offset through 031F 16 in the current data segment. -D F ( ) 微處理機原理與應用 Lecture Examining and Modifying the Contents of Memory Use the Dump command to examine the 16 bytes of memory just below the top of the stack. -D SS:FFEE FFFD ( ) 微處理機原理與應用 Lecture

17 4.4 Examining and Modifying the Contents of Memory ENTER Command (E) E ADDRESS [LIST] e.g. -E DS:100 FF FF FF FF FF ( ) -E DS:100 ( ) -1342:0100 FF. _ ( ) (Return to end) -E DS:100 ( ) -1342:0100 FF. _ (Space bar to continue) -1342:0100 FF. FF._ 微處理機原理與應用 Lecture Examining and Modifying the Contents of Memory Start a data entry sequence by examining the contents of address DS:100 and then, without entering new data, depress the - key. What happen? -E DS:100 ( ) 1342:0100 FF. _ Entering - causes the display of previous byte storage location 微處理機原理與應用 Lecture

18 4.4 Examining and Modifying the Contents of Memory Enter ASCII data to the memory. -E DS:200 ASCII ( ) -E DS:200 ASCII ( ) 微處理機原理與應用 Lecture Examining and Modifying the Contents of Memory FILL Command (F) The FILL command fills a block of consecutive memory locations all with the same data. F STARTING_ADDRESS ENDING_ADDRESS LIST e.g. -F F 22 ( ) 微處理機原理與應用 Lecture

19 4.4 Examining and Modifying the Contents of Memory Initialize all storage locations in the block of memory from DS:120 through DS:13F with the value and the block of storage locations from DS:140 to DS:15F with the value F F 33 ( ) -F F 44 ( ) 微處理機原理與應用 Lecture Examining and Modifying the Contents of Memory MOVE Command (M) The MOVE command allows us to copy a block of data from one part of memory to another part. M START_ADDRESS END_ADDRESS DEST_ADDRESS e.g. -M F 200 ( ) 微處理機原理與應用 Lecture

20 4.4 Examining and Modifying the Contents of Memory Fill each storage location in the block of memory from address DS:100 through DS:11F with the value Then copy this block of data to a destination block starting at DS:160. -F F 11 ( ) -M F 160 ( ) 微處理機原理與應用 Lecture Examining and Modifying the Contents of Memory COMPARE Command (C) The COMPARE command allows us to compare the contents of two blocks of data to determine if they are or are not the same. C START_ADDRESS END_ADDRESS DEST_ADDRESS e.g. -C F 120 ( ) 微處理機原理與應用 Lecture

21 4.4 Examining and Modifying the Contents of Memory COMPARE Command (C) Results produced when unequal data are found with a COMPARE command 微處理機原理與應用 Lecture Examining and Modifying the Contents of Memory SEARCH Command (S) The SEARCH command can be used to scan through a block of data in memory to determine whether or not it contains specific data. C START_ADDRESS END_ADDRESS LIST e.g. -S F 33 ( ) 微處理機原理與應用 Lecture

22 4.4 Examining and Modifying the Contents of Memory SEARCH Command (S) 微處理機原理與應用 Lecture Input and Output of Data INPUT Command (I) The INPUT command read data from an input port of the 64K byte-wide ports of 8088 I/O. I ADDRESS e.g. -I 61 ( ) 4D The contents of the port ant I/O address are 4D 微處理機原理與應用 Lecture

23 4.5 Input and Output of Data OUTPUT Command (O) The OUTPUT command write data to an input port of the 64K byte-wide ports of 8088 I/O. O ADDRESS BYTE e.g. -O 61 4F ( ) This command causes the value 4F 16 to be written into the byte-wide output port at address 微處理機原理與應用 Lecture Hexadecimal Addition and Subtraction HEXADECIMAL Command (H) The HEXADECIMAL command provides the ability to add and subtract hexadecimal numbers. H NUM1 NUM2 e.g. -H ABC0 0FFF ( ) BBBF 9BC1 -H BBBF A ( ) BBC9 BBB5 *Both number and results are limited to four hexadecimal digits 微處理機原理與應用 Lecture

24 4.6 Hexadecimal Addition and Subtraction Use the H command to find the negative of the number H 0 9 ( ) 0009 FFF7 FFF7 16 is the negative of 9 16 expressed in 2 s complement form 微處理機原理與應用 Lecture Hexadecimal Addition and Subtraction If a byte of data is located at physical address 02A34 16 and the data segment register contains , what value must be loaded into the source index register such that DS:SI points to the byte storage location? -H 2A ( ) 3F This shows that SI must be loaded with the value 微處理機原理與應用 Lecture

25 4.7 Loading, Verifying and Saving Machine Language Program An example to load an instruction MOV BL, AL The machine code is 88C3 16 -E CS: C3 ( ) -D CS: ( ) 1342: C 微處理機原理與應用 Lecture Loading, Verifying and Saving Machine Language Program UNASSEMBLE Command (U) The UNASSEMBLE command converts machine code instructions to their equivalent assembly language source statement. U [STARTING_ADDRESS [ENDING_ADDRESS] ] e.g. -U CS: ( ) 1342: C3 MOV BL, AL 微處理機原理與應用 Lecture

26 4.7 Loading, Verifying and Saving Machine Language Program Use a sequence of commands to load, verify loading, and unassemble the machine code instruction 0304H. Load the instruction at address CS:200. -E CS: ( ) -D CS: ( ) -U CS: ( ) ADD AX, [SI] 微處理機原理與應用 Lecture Loading, Verifying and Saving Machine Language Program WRITE Command (W) The WRITE command gives the ability to save data stored in memory on a diskette. W [START_ADDRESS [DRIVE START_SECTOR NUM_SECTOR] ] e.g. -W CS: ( ) -W ( ) Drive B 1 Sector = 512 Byte * Be caution in saving program in a disk, especially the hard drive 微處理機原理與應用 Lecture

27 4.7 Loading, Verifying and Saving Machine Language Program LOAD Command (L) The LOAD command gives the ability to reload memory from a diskette. L [START_ADDRESS [DRIVE START_SECTOR NUM_SECTOR] ] e.g. -L CS: ( ) The reloading of the instruction can be verified by U command e.g. -U CS: ( ) 1342: ADD AX, [SI] 微處理機原理與應用 Lecture Loading, Verifying and Saving Machine Language Program Enter the machine code of the block move program. The program is to be loaded into memory starting at address CS:100. Verify, unassemble, and save the code. -E CS:100 B E D8 BE BF B A ( ) -D CS: ( ) -U CS: ( ) -W CS: ( ) 微處理機原理與應用 Lecture

28 4.7 Loading, Verifying and Saving Machine Language Program 微處理機原理與應用 Lecture Loading, Verifying and Saving Machine Language Program NAME Command (N) The NAME command, along with the WRITE command, gives the ability to save a program on the diskette under a file name. N FILE NAME The BX, CX registers must be updated to identify the size of the program that is to be saved in the file. After BX, CX registers have been initialized, the write command is used to saved the program. To reload the program, the command sequence is N FILE NAME L [STARTING ADDRESS] 微處理機原理與應用 Lecture

29 4.7 Loading, Verifying and Saving Machine Language Program Save a machine code program into a file. -N A:BLK.1 ( ) ; Give a file name in disk A -R CX ( ) ; Give a program size of bytes CX XXXX :18 -R BX ( ) BX XXXX :0 ( ) W CS:100 ( ) ; Save the program in disk A 微處理機原理與應用 Lecture Loading, Verifying and Saving Machine Language Program Reload a program into memory. -N A:BLK.1 ( ) ; Give a file name in disk A -L CS:100 ( ) ; Load the program name BLK.1 in disk A C:\DOS>REN A:BLK.1 BLK.EXE ( ) ; Rename the file C:\DOS>DEBUG A:BLK.EXE ( ) ; Load the program directly C:\DOS>A:BLK.EXE ( ) ; Run the program 微處理機原理與應用 Lecture

30 4.8 Assembling Instructions with the Assemble Command ASSEMBLE Command (A) The ASSEMBLE command let us automatically assemble the instructions of a program. A [STARTING_ADDRESS] e.g. -A CS:100 ( ) 1342:0100 _ 1342:0100 ADD [BX+SI+1234], AX ( ) 1342:0104 _ -D CS: ( ) 微處理機原理與應用 Lecture Assembling Instructions with the Assemble Command Assemble a complete program with the ASSEMBLE command. -A CS:200 ( ) 0B35:0200 MOV AX, 2000 ( ) 0B35:0203 MOV DS, AX ( ) 0B35:0205 MOB SI, 100 ( ) B35:0217 NOP ( ) 0B35:0218 ( ) 微處理機原理與應用 Lecture

31 4.8 Assembling Instructions with the Assemble Command Assemble a program with ASSEMBLE command 微處理機原理與應用 Lecture Assembling Instructions with the Assemble Command Unassemble a program with UNASSEMBLE command 微處理機原理與應用 Lecture

32 4.9 Executing Instructions and Programs with the TRACE and GO command TRACE Command (T) The TRACE command provides the programmer with the ability to execute the program one instruction at a time. T [=STARTING_ADDRESS] [NUMBER] e.g. -T =CS:100 ( ) -T ( ) -T =CS:100 3 ( ) 微處理機原理與應用 Lecture Executing Instructions and Programs with the TRACE and GO command Load and trace a program. -L CS: ( ) -U ( ) -R AX ( ) AX 0000 :1111 ( ) -R SI ( ) SI 0000 :1234 ( ) -E DS: ( ) -T =CS:100 ( ) 微處理機原理與應用 Lecture

33 4.9 Executing Instructions and Programs with the TRACE and GO command 微處理機原理與應用 Lecture Executing Instructions and Programs with the TRACE and GO command GO Command (G) The GO command is typically used to run programs that are already working or to execute programs in the later stages or debugging. G [=STARTING_ADDRESS [BREAKPOINT_ADDRESS_LIST] ] e.g. -G =CS: ( ) -G =CS:100 ( ) -G ( ) 微處理機原理與應用 Lecture

34 4.9 Executing Instructions and Programs with the TRACE and GO command Use GO command to execute a program and examine the result. -N A:BLK.EXE ( ) ; Define the program file to be loaded -L CS:200 ( ) ; Load the program at CS:200 -R DS ( ) DS 1342 :2000 ( ) ; Define the data segment address -F DS:100 10F FF ( ) ; Fill memory with FF -F DS:120 12F 00 ( ) ; Fill memory with 00 -R DS ( ) DS 2000 :1342 ; Store data segment with 微處理機原理與應用 Lecture Executing Instructions and Programs with the TRACE and GO command Use GO command to execute a program and examine the result. (continued) -R ( ) ; Show data register status -U CS: ( ) ; Unassemble the program -G =CS:200 20E ( ) ; Execute the program to CS:20E -G =CS:20E 215 ( ) ; Execute the program to CS:215 -D DS:100 10F ( ) ; Display memory at DS:100 -D DS:120 12F ( ) ; Display memory at DS:120 -G =CS: ( ) ; Execute the program to CS:217 -D DS:100 10F ( ) ; Display memory at DS:100 -D DS:120 12F ( ) ; Display memory at DS: 微處理機原理與應用 Lecture

35 4.9 Executing Instructions and Programs with the TRACE and GO command 微處理機原理與應用 Lecture Executing Instructions and Programs with the TRACE and GO command 微處理機原理與應用 Lecture

36 4.9 Executing Instructions and Programs with the TRACE and GO command 微處理機原理與應用 Lecture Debugging a Program Errors in a program are also referred to as bugs; the process of removing them is called debugging. Two types of errors Syntax error Execution error A syntax error is an error caused by not following the rules for coding or entering an instruction. These types of errors are typically identified by the microcomputer and signaled to user with an error message In the DEBUG environment, the TRACE command is usually used to debug execution errors 微處理機原理與應用 Lecture

37 4.10 Debugging a Program Review of the DEBUG commands 微處理機原理與應用 Lecture