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erman86
 Post subject: 7 segment display
PostPosted: Sat Mar 15, 2008 5:19 am 
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Posts: 1
I am really a beginner..can anyone show me the simple way to display and 7 segment.give me a full instruction example..the simple one to display 12345678
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profkelly
 Post subject:
PostPosted: Sat Mar 15, 2008 11:32 am 
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Posts: 1102
The Examples folder of EASy68K contains a program named clockDigital.x68. The segment7 subroutine is in that program:
Code:
*-----------------------------------------------------------
*         A
*       -----
*     F|     |B
*      |  G  |
*       -----
*     E|     |C
*      |  D  |
*       -----   .H
*
* Bit Number  7 6 5 4 3 2 1 0
* Segment     H G F E D C B A

* bit patterns to form digits on readout
digits:
    dc.b  $3F           digit 0
    dc.b  $06           digit 1
    dc.b  $5B           digit 2
    dc.b  $4F           digit 3
    dc.b  $66           digit 4
    dc.b  $6D           digit 5
    dc.b  $7D           digit 6
    dc.b  $07           digit 7
    dc.b  $7F           digit 8
    dc.b  $6F           digit 9
    dc.b  $00           digit off
    dc.b  $40           dash

    ds.w  0             force word boundary

*----------------------------------------------------------
* Display a digit on the 7-segment display
* Pre:  D3.B contains 1 digit to display
*       A2 points to 7-segment LED to use
* Post: A2 points to next 7-segment LED

segment7:
    movem.l d3/a0,-(a7)     save registers
    lea digits,a0           bit pattern table
    and.l   #$00ff,d3
    move.b  (a0,d3),(a2)    display digit
    adda.l  #2,a2
    movem.l (a7)+,d3/a0     restore registers
    rts

Put the number you want to display in register D3, put the address of the seven segment display in register A2 and call segment7.

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lostin68k
 Post subject:
PostPosted: Mon Sep 21, 2009 5:38 pm 
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Joined: Wed Jul 08, 2009 11:24 pm
Posts: 14
Location: singapore
i triedd using the code to output 1 but it seems im doing something wrong. i cant see the number 1 and then i get the following error:
Address Error: Instruction at 103e accessing address fffff9.

ORG $1000
START: ; first instruction of program

move.b #32,d0 trap task to get address of hardware
move.b #0,d1
trap #15 display hardware window
move.b #1,d1
trap #15 get address of 7-segment display
move.l d1,a4 A4 = Address of 7-segment display
move.b #2,d1
trap #15 get address of LEDs
move.l d1,a3 A3 = Address of LEDs

digits:
dc.b $3F digit 0
dc.b $06 digit 1
dc.b $5B digit 2
dc.b $4F digit 3
dc.b $66 digit 4
dc.b $6D digit 5
dc.b $7D digit 6
dc.b $07 digit 7
dc.b $7F digit 8
dc.b $6F digit 9
dc.b $00 digit off
dc.b $40 dash
ds.w 0 force word boundary

segment7:
movem.l d3/a0,-(a7) save registers
lea digits,a0 bit pattern table
and.l #$00ff,d3
move.b (a0,d3),(a2) display digit
adda.l #2,a2
movem.l (a7)+,d3/a0 restore registers
rts

move.l a4,a2
move.b #1,d3
bsr segment7

END START ; last line of source
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profkelly
 Post subject:
PostPosted: Tue Sep 22, 2009 11:06 am 
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Posts: 1102
lostin68k wrote:
ORG $1000
START: ; first instruction of program

move.b #32,d0 trap task to get address of hardware
move.b #0,d1
trap #15 display hardware window
move.b #1,d1
trap #15 get address of 7-segment display
move.l d1,a4 A4 = Address of 7-segment display
move.b #2,d1
trap #15 get address of LEDs
move.l d1,a3 A3 = Address of LEDs

digits:
dc.b $3F digit 0
dc.b $06 digit 1
dc.b $5B digit 2
dc.b $4F digit 3


This is a common problem I see with my students. You have data in the middle of your program. The program begins execution at the START label. It will execute instructions until it reaches the digits: label and then it will try to execute the dc.b data as 68000 instructions. Always place data in a seperate area of memory. Take a look at the digital clock example.

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lee
 Post subject:
PostPosted: Tue Sep 22, 2009 11:16 am 
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Joined: Mon Dec 27, 2004 11:40 pm
Posts: 318
Oh bother! I was all ready to post this then saw your reply. Meh, I'll post it anyway.


Lostin68k
The problem is you have mixed your code and data together and, as a result, you end up with EASy68K trying to execute the data.

What you need to do is rearrange your code so it looks more like this ..

Code:
      ORG $1000

start

      * Your main program goes here then either ..

      MOVEQ       #9,d0             * halt simulator
      TRAP        #15

      * .. or if you want to run continuously ..

      BRA         start             * loop forever

* Now should come any subroutines and data


.. and that will at least execute what you intend instead of trying to execute the data statements.

Lee.

Quote:
This is a common problem I see with my students. You have data in the middle of your program.

It probably doesn't help that the quick start guide programs also do this.

Lee.
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profkelly
 Post subject:
PostPosted: Wed Sep 23, 2009 9:45 pm 
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Posts: 1102
lee wrote:
Oh bother! I was all ready to post this then saw your reply. Meh, I'll post it anyway.

Sorry Lee, I appreciate the feedback you provide on this forum. Please keep it up.

Quote:
It probably doesn't help that the quick start guide programs also do this.

See I said it was a common problem. The quick start guide was written by two students. Thanks for pointing that out. I'll correct the code in the guide.

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lostin68k
 Post subject:
PostPosted: Thu Sep 24, 2009 2:04 am 
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Joined: Wed Jul 08, 2009 11:24 pm
Posts: 14
Location: singapore
thanks!
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