> Van: G345CDE <G345CDE@AOL.COM>
> Aan: PICLIST@MITVMA.MIT.EDU
> Onderwerp: Re: Reasonably simple schematics for PIC
> Datum: woensdag 6 mei 1998 22:18
>
> Hi:
> I am trying to learn to program the 16C84..I have a programmer but need
source
> code for a few relatively simple circuits to practice on......a counter
and  7
> seg. display counting to 9....anything that will help me visualize the
> relationship of the code to circuit action.  Open to all suggestions.
Thanks
> .  Regards,  George.

Hello George,

  You can do two things :  Use the PIC as a counter only (and decode your
counter-value external with a 7447 or alike) or do both in the PIC (count
and Binary-to-7Seg converson).  Thinking you will do the latter (why use
extra chips if you dont _have_ to :-) the hardware is shockingly simple :
just connect segments  'a' thru 'g' and the 'dp' thru some resistors of 470
Ohm (1K Ohm if you got a High-brightness display) to the I/O lines 0 thru 7
of port B.  This way you can turn every segment On-and-Off to your likings.

I suggest to use a common Kathode display (the common pin connected to
Ground). this way a '1' in the Output-data will turn a segement On.  If you
use a common Annode display (the common pin connected to VCC) a '0' will
turn the segment on.

Now the software : Put Port B int an Output by writing all zero's to the
TRISB-register. (don't forget to set & clear STATUS,RPO to do this !).  Now
send any
data to PORTB and your display will show the code (Try b'01101101' to get
the number 5 on the display).
To convert the values '0' thru '9' to the codes that will represent the
numbers
0 thru 9 on your display you will have to do something like :

  clrf PCLATH         ;Set the page your Bin7Seg-table is on
  movf COUNT,W    ;Copy Counter-value to W
  call Bin7Seg        ;Convert to 7-segment-code
  movwf PORTB     ;Send it to your Hardware


Bin7Seg:
  addwf PCL
  retlw b'????????'  ;Code for a 7-segment '0'
  retlw b'????????'  ;Code for a 7-segment '1'
            etc
  retlw b'01101101'  ;Code for a 7-segment '5'
            etc
  retlw b'????????'  ;Code for a 7-segment '9'

Warning : The table has only got items 0 thru 9, so the value in W should
_NOT_ exeed this max value. otherwise unexpected results will occur !

To see the next number : Advance COUNTER, call the Conversion-routine and
send the result again to PORTB

Don't forget to tell you program where you COUNTER variable is located
(preferrably at the first free RAM-location, 0x0C)

Greetz,
  Rudy Wieser

P.s.
  Extend your Bin7Seg-table to 16 elements (and have a Hexa-Decimal
display) and you could 'and' the upper nibble out so you can't get out of
the table.

Bin7Seg:
  andlw 0x0f
  addwf PCL
  retlw b'????????'  ;Code for a 7-segment '0'
         etc
  retlw b'????????'  ;Code for a 7-segment '15' (mostly the letter 'F')