Assembly and Interface Technology Experiment 6 - ADDA conversion experiment, AD acquisition system in interrupt mode

One 、 The experiment purpose

The experiment used 8259A,ADC0809, Digital tube to complete the design of a data acquisition system , The purpose is to understand the interrupt mode A/D Implementation method of data collection , Master the hardware design and the writing method of interrupt program , It is the training of students' comprehensive experimental ability .

Two 、 Experimental content

Use ADC0809 The passage of 0, Access 0-5V DC voltage of , use “ DC signal ” The potentiometer adjusts the analog voltage value ,A/D End of conversion signal EOC Connected to the main 8259A Of MIR3 On , collection 100 Data and store it in memory , At the same time, the collected 16 Hexadecimal data is displayed on the nixie tube . Please adjust it many times 0-5V The voltage value of （ Whirl “ DC signal ” knob ）, Conduct A/D collection , And observe the changes of data in memory .

3、 ... and 、 Experimental phenomena

Every time I collect 100 Data may be the same （ The data of the nixie tube may also remain unchanged ）, When “ DC signal ” Different data can be collected when the knob is rotated .

Four 、 Experimental wiring diagram

5、 ... and 、 The experimental steps

1、 Connect the experimental circuit correctly according to the schematic diagram （ Need to connect the red line ）.
The circuit diagram is as follows ：

2、 Correctly understand the experimental principle .
take 298H As a result of A/D0809 The port of , take 280H As a result of 8255A The port of .
take A/D0809 At the end of data conversion EOC High level of as 8259A The interrupt source of , Connected to MIRQ3, Of the main film IR3. in addition 8255A Of A Mouth in 0 Output segment code in mode ,B Mouth in 0 Output bit code in mode , Make the nixie tube display .
The flow chart of the main program is as follows ：

Flow chart of interrupt service program ：

3、 Write the experimental program , And debugging on the computer , Observe the results of the experiment .
The experimental procedure is as follows ：

STACKS   SEGMENT 
STA       DW 512 DUP(?)
TOP       EQU  LENGTH STA
STACKS     ENDS

DATA        SEGMENT
IO0809A     EQU       298H
LED         DB        3FH,06H,5BH,4FH,66H,6DH,7DH,07H,7FH,6FH,77H,7CH,39H,5EH,79H,71H
TMP_1        DB    ?
TMP_2        DB    ?
TMP          DB    ?
DATA        ENDS

CODE         SEGMENT
ASSUME CS:CODE,DS:DATA,SS:STACKS
START:
    MOV AX,CS
    MOV DS,AX
    MOV DX,OFFSET INT3      ; System function call 、 Set interrupt vector 、 from DS:DX Point to four byte address 
    

    MOV AX,250BH         ; AL= Interrupt type number （=0BH---0B*4= Vector table address ）
    INT 21H                ; ( Realize adding INT3 The address of )
    
    MOV DX,283H     ;8255 Command port address , To initialize 
    MOV AL,10001001B ; Set the way it works ,A Working in 0 Mode input ,B mouth 0 Mode output 
    OUT DX,AL
    
    MOV  AX,STACKS     ; Set the stack segment register SS
    MOV  SS,AX
    MOV  SP,TOP        ; Set stack pointer SP Initial value of 
    
    IN AL,21H              ; Set interrupt mask word （ use " read - And - Write " Mode enable ）
    AND AL,0F7H            ; Can make IRQ3
    OUT 21H,AL             ; write in OCW1( Shielded word )
    MOV  SI,0             ; Create a logo , original =0
    
    MOV  AX,DATA
    MOV  DS,AX
    MOV  DX,IO0809A      ; start-up A/D converter 
    OUT  DX,AL
LOOP1:
    STI                     ; Open the interrupt （IF Set up 1）
    IN   AL,DX
    MOV    CX,0FFFFH        ; Set the delay constant  
    CMP    SI,01           ; Search mark 、 Judge whether the conversion is completed 
    JNE LOOP1               ; Unfinished ： Return to wait 
LOOP3:    
    LOOP  LOOP3            ; When the conversion is completed, first delay    
    CLI
    MOV  DX,IO0809A        ; Start again A/D converter 
    OUT  DX,AL 
    JMP  LOOP1             ; Return to continue waiting for the next interrupt 

INT3:
    PUSH  AX                       ; Interrupt service routine 
    PUSH  DX
    PUSH  CX     
    MOV SI,1                   ; Create a sign that the conversion is complete （SI=1）
    MOV  DX,IO0809A
    IN   AL,DX                 ; from A/D Converter input data 
 ; Process the collected data ： take 8 Binary number is split into two hexadecimal numbers for display 
    MOV  TMP,0
    MOV     TMP,AL                 ; take AL Save to BL
    MOV  CL,4
    SHR  AL,CL                 ; take AL Shift four places to the right 
    CALL DISP1                  ; Adjust the display subroutine to display its upper four digits 
    MOV  AL,TMP
    AND  AL,0FH
    CALL DISP2                  ; Adjust the display subroutine to display its lower four digits 
    MOV  DL,20H               ;（ Space character ）
    INT  21H
    
    MOV  DL,20H               ;（ Space character ）
    INT  21H
    PUSH DX
    MOV  AH,06H              ; Determine whether a key is pressed 
    MOV  DL,0FFH               ;DX=FF when   The input character 
    INT 21H                    ;AL= Characters entered 
    POP DX
    JE   LOOP2                 ; If there is no keyboard operation （AL=0） Then turn START
    IN AL,21H                   ; Interrupt mask word OCW1 operation         ;
    OR AL,08H                   ; take IMR Medium IRQ3 shielding 
    OUT 21H,AL
    MOV  AH,4CH               ; sign out 
    INT  21H    
LOOP2:
    STI                         ; Interrupt before returning to the main program 
    MOV AL,20H                 ; Write OCW2, Hair EOI command 
    OUT 20H,AL                  ; send ISR The corresponding bit is cleared 
    POP CX
    POP DX
    POP    AX
    IRET                        ; Interrupt return 
    
DISP1  PROC NEAR                 ; Display subroutine 
    MOV  TMP_1,AL    

    MOV AL,00H
    MOV DX,281H            
    OUT DX,AL


    MOV  AL,TMP_1
    MOV  BX,OFFSET LED      ;BX Is the starting address of the digital table 
    XLAT                          ; Find out the corresponding segment code 
    MOV  DX,280H        ; from 8255 Of A output 
    OUT  DX,AL
    
    MOV AL,02H
    MOV DX,281H            ;
    OUT DX,AL
    RET
DISP1 ENDP    

DISP2  PROC NEAR                 ; Display subroutine 
    MOV  TMP_2,AL

    MOV AL,00H
    MOV DX,281H;
    OUT DX,AL
    
    MOV  AL,TMP_2
    MOV  BX,OFFSET LED      ;BX Is the starting address of the digital table 
    XLAT                          ; Find out the corresponding segment code 
    MOV  DX,280H        ; from 8255 Of A output 
    OUT  DX,AL
    
    MOV AL,01H
    MOV DX,281H            ;
    OUT DX,AL
    RET
DISP2 ENDP 
CODE ENDS
END START

Experimental results and problems encountered ：

Although the setting is output on the two digit nixie tube , But because the nixie tube can only output one bit at a time , And considering the fluctuation of the data , So we didn't set the delay in the program , It is hoped that the real data situation can be presented through high-frequency data display .
Our experimental box has good performance , So in the process of the experiment, we can observe from 00 To FF Complete data range , The above figure shows the maximum value , But because the data flashes too fast , There is only one in the photo F.
During the experiment , One of the main difficulties encountered is the display of digital tubes , This is found online XLAT Instructions , Can be BX + AL And send the results to AL,LED Is an array previously defined in the data segment , What is stored is the segment code representation of a series of numbers ,BX yes LED The offset address of , that BX + AL Namely AL The address of the hexadecimal segment code corresponding to this binary number , Deliver to A You can get the correct digital display by speaking .