Experiment 6 8255 parallel interface experiment [microcomputer principle] [experiment]

Preface

The following contents are derived from the microcomputer principle experiment guide
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8255 Parallel interface experiment

3.2 8255 Parallel interface experiment

3.2.1 The experiment purpose

1、 master 8255A Parallel connection 1 The basic structure and working principle of the chip .
2、 master 8255A Operation mode 0 The characteristics and usage of .
3、 master 8255A The port of A Or port B Work in a way 1 The characteristics and usage of ; Master the way 1 Input or output port C Definition and function of pin used as contact signal .
4、 The method of solidifying and running the program offline .

3.2.2 Experimental content

1、 Basic input and output experiments . Programming , send 8255A Of A The mouth is the output ,B The mouth is the input , Complete the data transmission from the toggle switch to the data lamp . As long as the switch is turned , The display of the data lamp changes .
2、 Water lamp display experiment . Programming , send 8255 Of A Mouth and B All ports are output , Realization 16 Relative cycle display of bit data lamp .
3、( Choose to do ) The way 1 I / O experiment . Programming , send 8255 Work in the way 1 Under control A I want to input ,B output .

3.2.3 Experimental principle

The parallel interface is based on the byte of data I/O Transfer information between devices or controlled objects .CPU Data transfer between and interfaces is always parallel . That is, it can be transmitted at the same time 8 position 、16 position 、32 I'm waiting for you .8255 The programmable peripheral interface chip is Intel The general parallel produced by the company I/O Interface chip , It has A、B、C Three parallel interfaces , use +5V Single power supply , Can work in the following three ways : The way 0– Basic input / Output mode 、 The way 1- Strobe input / output mode 、 The way 2- Two way strobe working mode .8255 The internal structure and pins of the are shown in the figure 3-2-1 Shown ,8255 Working mode control word and C The mouth is positioned according to the position / The format of reset control word is shown in the figure 3-2-2 Shown .

8255 The circuit diagram of the experimental unit is shown in the figure 3-2-3 Shown .

3.2.4 Experiment description and steps

1、 Basic input and output experiments
This experiment makes 8255 port A Work in the way 0 And as an output port , port B Work in the way 0 And as an input port . Use a set of switch signals to access the port B, port A The output line is connected to a group of data lamps , And then through the right 8255 Chip programming to achieve input and output functions . The specific experimental steps are as follows , Among them the first (4) Step to step (6) The step curing function can be selected as :
(1) The experimental wiring diagram is shown in Figure 3-2-4 Shown , Connect the experimental circuit diagram according to the figure .
(2) Write the experimental program , Compiled 、 Load the system after the connection is correct .
------------ Theoretical knowledge -----------
1、 Confirm the port address

IO Base address 0600H
XR1---A0
XR2---A1
 Address range 600H~603H
 port A Address ：0600H
 port B Address ：0602H
 port C Address ：0604H
 Control register port address ：0606H

2、 Determine how it works

 port A Work in a way 0, Basic output mode 
 port B Work in a way 0, Basic input mode 

3、 Determine the control word

1 00  0 x 0 1 x

4、 Initializer

A EQU 0600H
B EQU 0602H
C EQU 0604H
S EQU 0606H
CODE SEGMENT
	ASSUME CS:CODE
START:
	; Set port A, The way 0 Output 
	; Set port B, The way 0 Input 
	MOV AL,10000010B
	MOV DX,S      ; Send control word 
	OUT DX,AL
	
NEXT:	
	; from B Read the switch status through the port 
	; Will be taken from B The switch state read by the port 
	; Send to port A Output 
	MOV DX,B              ; read B The starting data sent by the port ,B I want to input  
    IN AL,DX 
    MOV DX,A               ; Write A The starting data sent by the port ,A output  
    OUT DX,AL 
    
	; Press the no key 
	MOV AH,1                   
    INT 16H 
	JNZ QUIT
		
	JMP NEXT
	
QUIT:	
	MOV AH,4CH
	INT 21H
CODE ENDS
	END START

------------ Theoretical knowledge -----------

------------ Concrete practice -----------

8255 Parallel interface experiment

IOY0 EQU 0600H               ;8255 Of CS Pin connection IOY0 Corresponding port start address  
MY8255_A EQU IOY0+00H*2 ;          ;8255 The port of A Address  
MY8255_B EQU IOY0+01H*2           ;8255 The port of B Address  
MY8255_C EQU IOY0+02H*2           ;8255 The port of C Address  
MY8255_MODE EQU IOY0+03H*2      ;8255 Control register address of  
CODE SEGMENT                     ; Define code snippets  
    ASSUME CS:CODE 
START: MOV DX,MY8255_MODE       ;8255 The control port address is 3006H 
    MOV AL,82H  ; Set up 8255 Mode control word ,A、B How mouth works 0,A output ,B I want to input  
    OUT DX,AL 
LOOP1: MOV DX,MY8255_B            ; read B The starting data sent by the port ,B I want to input  
    IN AL,DX 
    MOV DX,MY8255_A               ; Write A The starting data sent by the port ,A output  
    OUT DX,AL 
    MOV AH,1                        ; Determine whether a key is pressed  
    INT 16H 
    JZ LOOP1                        ; If there is no key, it will jump back to continue the cycle , If there is one, quit  
QUIT: MOV AX,4C00H                 ; End program exit  
    INT 21H 
CODE ENDS 
    END START 

------------ Concrete practice -----------

(3) Run the program , Change the observation after the toggle starts LED Show , Verify program functions
(4) Click on “ debugging ” In the drop-down menu “ Curing process ” term , Solidify the program into the system memory
(5) take 386EX Short circuit jumper of single board computer system JDBG Every control to RUN End , Then press the reset button , Observe whether the program works normally ; Turn off the power supply of the test box , After a while, open the tester again , See whether the solidified segment sequence is running , Verify program functions
(6) After the experiment , Please place the short-circuit jumper DRG The short-circuit block of is short circuited to DBG End , To facilitate the next online experiment .

tip :I386E CPU The single board computer supports online debugging mode and offline independent operation mode . The switching between the two modes is through I386EX CPU The short-circuit jumper at the lower substrate at the lower right corner of the single board computer unit JDBG To achieve , The short circuit block is short circuited to DBG When ,CPU In online debugging mode with the software , In this mode , Through the software industry, we can find CPU Download the program , Single step 、 The breakpoint 、 Continuous operation and other commissioning , Through the curing function menu , Can be loaded into CPU The solidified program in the memory of a single board computer goes to FLASH In the memory . After curing , Short the short-circuit block to RUN files , And reset or power on ,CPU Will start FLASH The program in memory runs independently , here I386EX CPU The single board computer works in the offline independent operation mode

2、 Water lamp display experiment
send 8255 Of A Mouth and B All ports are output , Data lamp D7 ~ D0 From left to right , Only one light at a time , Cycle show ,D15~ D8 And D7~D0 Just the opposite , From right to left , Only one light at a time , Cycle show . The experimental wiring diagram is shown in Figure 4.3.5 Shown . The experimental steps are as follows :
(1) According to the figure 3-2-5 Connect the experimental circuit diagram .
(2) Write the experimental program , Compiled 、 Load the system after the link is correct .
------------ Theoretical knowledge -----------
1、 Confirm the port address

IO Base address 0600H
XR1---A0
XR2---A1
 Address range 600H~603H
 port A Address ：0600H
 port B Address ：0602H
 port C Address ：0604H
 Control register port address ：0606H

2、 Determine how it works

 port A Work in a way 0, Basic output mode 
 port B Work in a way 0, Basic output mode 

3、 Determine the control word

1 00  0 x 0 0 x

4、 Initializer

A EQU 0600H
B EQU 0602H
C EQU 0604H
S EQU 0606H
CODE SEGMENT
	ASSUME CS:CODE
START:
	; Set port A、B The way 0 Output 
	MOV AL,10000000B
	MOV DX,S      ; Send control word 
	OUT DX,AL
	
INIT:	
	MOV BL,7FH
	MOV CL,0FEH
	
	;A Input the value through the port 1(7FH)
	;B Input the value through the port 2(FEH)
NEXT:	
	MOV DX,A
	MOV AL,BL
	OUT DX,AL
	
	MOV DX,B
	MOV AL,CL
	OUT DX,AL
	
	; Press the no key 
	MOV AH,1                   
    INT 16H 
	JNZ QUIT
	
	; The number 1 Move right , The number 2 Move left 
	ROR BL,1
	ROR CL,1
	
	
	
	JZ INIT
	JNZ NEXT
	
QUIT:	
	MOV AH,4CH
	INT 21H
CODE ENDS
	END START
	

------------ Theoretical knowledge -----------

------------ Concrete practice -----------
8255 Do the running water lamp experiment

CODE SEGMENT
     ASSUME CS:CODE
START: 
	   MOV DX,606H
       MOV AL,80H;A Port selection 00 The way ,B mouth 0 The way 
       OUT DX,AL; Send control word 
       MOV CL,80H ; Assign initial value to 
       MOV BL,1H ; Assign initial value to 
 AA1:
    	MOV DX,600H 
        MOV AL,CL
        OUT DX,AL
        MOV DX,602H
        MOV AL,BL
        OUT DX,AL
        CALL DELAY ; Delayed action 
        ROL BL,1H  ; Cycle one bit left 
        ROR CL,1H  ; Cycle right one bit 
        JMP AA1
DELAY:
  		PUSH CX
        MOV CX,0FFFFH
  	    AA2:PUSH AX
	       POP AX
	       LOOP AA2
	    POP CX
	   
       RET
       
  CODE ENDS
       END START

------------ Concrete practice -----------
(3) Run the program , Observe LED The light shows , Verify program functions .
(4) Change the way of running water lamp by yourself , Programming .
(5) Solidify the program and run it offline ( Optional ).

3、 The way 1 I / O experiment ( Optional )
This experiment makes 8255 port A Work in the way 0 And as an output port , port B Work in the way 1 And as input , Then port C Of PC2 Become a strobe signal input STBB,PC0 Become the interrupt request signal output terminal INTRB, When B After the port data is ready , By sending STBB Signal to request CPU Read port B Data is sent to the port A The output shows . Use a set of switch signals to access the port B, port A The output line is connected to a group of data lamps . The specific experimental steps are as follows :

(1) According to the figure 3-2-6 Connect the experimental circuit diagram .
(2) Write the experimental program , Compiled 、 Load the system after the link is correct .

------------ Theoretical knowledge -----------

1、 Confirm the port address

IO Base address 0600H
XR1---A0
XR2---A1
 Address range 600H~603H
 port A Address ：0600H
 port B Address ：0602H
 port C Address ：0604H
 Control register port address ：0606H

2、 Determine how it works

 port A  The way 0  Output 
 port B  The way 1  Input 

3、 Determine the control word

1 00 0 x 1 1 1

4、 Initializer

A EQU 0600H
B EQU 0602H
C EQU 0604H
S EQU 0606H
CODE SEGMENT
	ASSUME CS:CODE
START:
	; Set port A, The way 0 Output 
	; Set port B, The way 1 Input 
	MOV AL,10000111B
	MOV DX,S      ; Send control word 
	OUT DX,AL
	
	MOV DX,B
	IN AL,DX
	
	MOV DX,A
	OUT DX,AL

	
	
	MOV AH,4CH
	INT 21H
CODE ENDS
	END START

------------ Theoretical knowledge -----------
(3) Run the program , Then change the toggle switch , When you're ready , Press KK1, At the same time, observe the data lamp display , It shall be consistent with the switchpack signal

3.2.5 Experimental tips

1、 The flow chart of basic input and output experiment procedure is shown in Figure 3-2-5 Shown ;
2、 The flow chart of the flow lamp display experiment procedure is shown in Figure 3-2-6 Shown :

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