EKT 222 MICROPRESSOR SYSTEM. LAB 4 Extra : INTERFACING WITH OTHER I/O DEVICES

Transcription

1 EKT 222 MICROPRESSOR SYSTEM LAB 4 Extra : INTERFACING WITH OTHER I/O DEVICES

2 LAB 4 Extra: Interfacing with Other IO devices Objectives: 1) Ability to create advance program instructions 2) Ability to use branching instructions 3) Ability to execute and demonstrate the program instructions 4) Ability to analyze the 8085 register and memory map conditions Equipments : 1. Computer station with Windows OS and MY simulation program Instruction Sets (Assembly Code) Instruction Sets (Machine Code) Introduction The 8085 simulator program MY1 Sim85, has several built-in input output graphical user interfaces (GUIs) developed for the users practice. Although not exactly accurate as in the actual hardware input and output devices, but these graphical interfaces do offer the user some added value demonstration materials in understanding their program further. One can especially observe their simulation program and analyze on any assembly code improvements. Table 1 below lists out the available IO GUIs and its operating procedures: No GUI Device Panel Description 1 8 LEDs (output) & 8 LEDs aligned in one row in one panel. There are two panels available. The horizontal panel and the vertical panel. Each LED requires logic HIGH to illuminate. Direct usage bit to LED representation. 2 8 switches (input) 8 push-pull type switches aligned in one row. When in pushed-up condition (red color), it gives logic LOW and when pulled-down (blue color), it gives logic HIGH. Direct bit to switch representation. 3 8 pushbuttons (input) 8 pushbuttons in one panel. When depressed (red color) gives logic LOW and when pressed (blue color) gives logic HIGH. Direct bit to button representation. 1

3 4 7-segment LED (output) 7-segment LED active high panel. Requires 8-bit data to send and operate the desired segment. Direct pin to LED representation. 5 4x4 Keypad (input) 16 button panel using the 4x4 matrix. Using 5-bit signals, 2 bit column, 2 bit row and one bit acknowledge sent into the processor. The acknowledge signal, DA will assert (logic HIGH) upon valid keypress together with the 4x4 bit matrix data. The data will stay present after the key is released until another key is pressed. DA - Data Acknowledge D3 & D2-2-bit ROW data (00 ~ 11) D1 & D0-2-bit COLUMN data (00 ~ 11) Table 1 : My1 Sim85 IO Panels In this extra lab activity, students will be demonstrated on 1. How to display data onto the 7-segment LED 2. How to use the 4x4 keypad 2

4 LABORATORY TASK Part A : INTERFACING THE 7-SEGMENT LED Given below is a sample program on how to display a BCD counter on a 7-segment LED. Take note of the string of data sent to PORT A. ORG 0000H LXI SP,3FF0H ; stack memory setting PORTA: EQU 80H ; set 80H with a name PORTB: EQU 81H ; PORTC: EQU 82H ; CTRL: EQU 83H ; MVI A,80H ; set the port directions OUT CTRL ; send to control register AGAIN: MVI B,10 ; create an internal counter at B LXI H,TABLE ; set HL with memory pointer COUNT: MOV A,M ; get data from memory pointer OUT PORTA ; send out to 7-segment MVI C,20 ; create a delay value at C DELAY: DCR C ; decrease C JNZ DELAY ; jump to delay if C 0 INX H ; if C = 0 then increase HL DCR B ; decrease B counter JNZ COUNT ; if B 0, continue count up JMP AGAIN ; if B = 0 reset B counter HLT TABLE: B, B, B, B, B B, B, B, B, B As you can see, the Table s 8-bit values were prepared to illuminate the necessary LED segments. 3

5 Part B : INTERFACING THE KEYPAD Given below is a sample program to display the BCD value of a keypad on the 7- segment LED. Values above 9 will cause the 7-segment LED to display E rror. Take note of the string of data sent to PORT A. ORG 0000H LXI SP,4000H PORTA: EQU 80H PORTB: EQU 81H PORTC: EQU 82H CTRL: EQU 83H MVI A, B ; Port A (output), Port B (input) OUT CTRL MVI A,00H ; clear 7-segment OUT PORTA CHECK1: IN PORTB ; check for valid key press ANI 10H JZ CHECK1 CHECK2: IN PORTB ; check for valid key release ANI 10H JNZ CHECK2 LXI H,DATA ; set HL with memory pointer MVI B,0 ; set B register with 00H IN PORTB ; get keypad data MOV C,A ; copy to C register DAD B ; add HL with BC contents & store in HL MOV A,M ; get data from new HL memory pointer OUT PORTA ; display to 7-segment JMP CHECK1 ; jump to check1 HLT DATA: B, B, B, B B, B, B, B B, B, B, B B, B, B, B As you can see, the program will check if a key is pressed (DA=1) before that key is released (DA=0). This process will justify a valid keystroke. 4

6 EXERCISE 1. Create a program that will display the BCD value of a 4-bit switch on a 7- segment LED. Use the BCD data string table from the Laboratory Task as reference. 2. The BCD counter in Laboratory Task Part A counts on every clock pulse supplied by the simulator software. Recreate the program so that the counter will count on every clock pulse pressed by a PUSH BUTTON. 3. Create a program that will blink an LED according to the count of the keypad value. For example if the key 5 is pressed, then the LED will blink 5 times AFTER a PUSH BUTTON is pressed. 4. Create an up-down BCD counter with the following sequence : 0 -> 1 -> 2 -> -> 8 -> 9 -> 8 -> 7 -> -> 2 -> 1 -> 0 5. Create a program that will store 4 digits and then display the digits in sequence on a 7-segment LED. 6. Using 2 push-pull switches, create a program that will fulfill the following operation : a. 00 the 7-segment displays 0 only b. 01 the 7-segment will do a BCD continuous up count c. 10 the 7-segment will do a BCD continuous down count d. 11 the 7-segment will pause counting 5