Seven segment interfacing with 8051.pdf
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This document discusses interfacing a 7-segment display with an 8051 microcontroller. There are two common types of 7-segment displays - common cathode and common anode. An 8051, 7-segment display, 2-4 decoder, transistors, and power supply are needed. Lookup tables store the segment patterns for digits 0-9 depending on the display type. Assembly code samples show how to display digits on one or four 7-segment displays by selecting the correct display using a 2-4 decoder connected to ports on the 8051.
Seven segment interfacing with 8051.pdf
- 1. Seven Segment Interfacing with 8051 T.Srikrishna, M.Sc, M.Tech, GVP Seven segment interfacing with 8051 The name 7 segments imply there are 7 LED segments arranged as shown Seven segment displays are used to display digits from 0 to 9 and they also display letters A to F Working There are two main constructions of the seven-segment display modules Common Cathode: In this type of segments all the cathode terminals are made common and tied to GND. Thus the segments a to g needs a logic High signal(5v) in order to glow. Common Anode: In this type of segments all the anodes terminals are made common and tied to VCC(5v). Thus the segments a to g needs a logic LOW signal(GND) in order to glow.
- 2. Seven Segment Interfacing with 8051 T.Srikrishna, M.Sc, M.Tech, GVP Components required 8051 Microcontroller 7-Segment-Display 2:4 Decoder NPN bipolar junction transistor – 5V Power supply
- 3. Seven Segment Interfacing with 8051 T.Srikrishna, M.Sc, M.Tech, GVP We will have two lookup tables that have values that are the complement of each other depending on whether we are using common anode/common cathode type seven-segment display.
- 4. Seven Segment Interfacing with 8051 T.Srikrishna, M.Sc, M.Tech, GVP Assembly language program to interface seven segment display (0-9) ORG 4000H DB: 3FH, 06H, 5BH, 4FH, 66H, 6DH, 7DH, 07H, 7FH, 6FH, 0 ; Lookup table for digits 0 to 9 ORG 0000H main: MOV DPTR, #4000H Repeat: CLR A MOVC A, @A+DPTR ; Copy data from external location to accumulator MOV P1, A ; Move the pattern of the digit into port P2 ACALL delay ; Call a delay to so that the transition is visible INC DPTR ; Point to the next pattern CJNE A, 0, Repeat ; Repeat till 0 (Stop bit) is received SJMP main ; Run this forever till externally stopped
- 5. Seven Segment Interfacing with 8051 T.Srikrishna, M.Sc, M.Tech, GVP Mode P3.4 P3.3 Active Module 1 0 0 1 2 0 1 2 3 1 0 3 4 1 1 4
- 6. Seven Segment Interfacing with 8051 T.Srikrishna, M.Sc, M.Tech, GVP Seven segment display – Four Modules Now to interface more than one module at once with the 8051 microcontroller. Hence, we connect a 2:4 decoder, whose inputs are given by pin P3.3 and pin P3.4. Based on the status of these two pins, we come up with four modes that correspond to the display selected. Assembly language program to interface quad seven segment displays to 8051 ORG 4000H DB 06H, 5BH, 4FH, 66H ORG 0000H main: MOV DPTR, #4000H MOV P3, #00H ; clear the port 3 to use it as output port CLR P3.3 ; Mode 1 CLR P3.4 ; 00 CLR A MOVC A, @A+DPTR CPL A MOV P2, A ; P2 = 00000110b = pattern of digit ‘1’ ACALL delay INC DPTR SETB P3.3 ; Mode 2 CLR P3.4 ; 01 CLR A MOVC A, @A+DPTR
- 7. Seven Segment Interfacing with 8051 T.Srikrishna, M.Sc, M.Tech, GVP CPL A MOV P2, A ; P2 = 01011011b = pattern of digit ‘2’ ACALL delay INC DPTR CLR P3.3 ; Mode 3 SETB P3.4 ; 10 CLR A MOVC A, @A+DPTR CPL A MOV P2, A ; P2 = 01001111b = pattern of digit ‘3’ ACALL delay INC DPTR SETB P3.3 ; Mode 4 SETB P3.3 ; 11 CLR A MOVC A, @A+DPTR CPL A MOV P2, A ; P2 = 01100110b = pattern of digit ‘4’ ACALL delay SJMP main ; Run this program forever