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 2.3.7. Writing multi character on 8 x 7 segment

In this lesson, we are going to drive more 7 segmen, in this way you can write eight character on 8 x 7 segmen. We used a multiplexing methode to transfer data for driver transistor consequtively. Another mothode to take the data tobe transfer to 8 x 7 segment is by used look up table, as shown in listing program below.

Step 1st
Build the circuit as shown in figure 2.3.5. As you seen on figure 2.3.5. P2.0 trough P2.7 is connected to driver transistor, and all eight 7 segment is connected to P0.0 trough P0.6 parallelly. Remember, that all we want to do with this lesson is write multi character ( A-b-C-d-E-F-g-h ) to 1st, 2nd, 3rd, 4th, 5th, 6th, 7th and 8th 7 segmen each.

Step 2nd
In this step, you must tipe the assembly program to make your 7 segmen shown some number on 7 segmen, we assume that you have already known the editor, we used MIDE-51 to edit the program. ( Download File : exp237.zip , Download Complete Circuit File : Sevensegmen.PDF )

       org 0h
start: mov dptr, #word  ;get dptr address
       mov R6,#8        ;save number of character
       mov R1,#01111111b;drive for 8th 7 segment
Again: clr A            ;clear A, A= 0 
       movc A,@A+dptr   ;take data from look up table
       inc dptr         ;inc address
       mov P0,A         ;write character to P0
       mov A,R1         ;transfer data R1 -> A
       mov P2,A         ;send data A to P2
       rr A             ;rotate right data A
       mov R1,A         ;saving data A -> R1
       call delay       ;call delay time
       mov P0,#11111111b;
       djnz R6,Again    ;decrement number character
       sjmp start       ;jump forever
;=============================================
;subroutine delay created to rise delay time
;=============================================
delay: mov R1,#255
del1:  mov R2,#255
del2:  djnz R2,del2
       djnz R1,del1
       ret
;
word:  DB 00111111b, 01000111b, 00001000b, 00000011b
       DB 01000110b, 01000000b, 01001000b, 00111111b
       end

Step 3rd
Safe your assembly program above, and name it with 7seg5.asm (for example) Compile the program that you have been save by using MIDE-51, see the software instruction.

Step 4th
Download your hex file ( 7seg5.hex ) into the microcontroller by using Microcontroller ATMEL ISP software, see the instruction.After download this hex file you'll see the action of the 7 segmen( of course if your cable connection and your program are corrected ).

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