PIC 16f887 internal clock help needed

[lockjawz]

I'm very new to this pic and programing all together and i need some help. Can some one help me setting up my internal clock on my 16f887 chip.

[mackrackit]

This is a good place to start reading to find out how to setup fuses.
http://www.picbasic.co.uk/forum/showthread.php?t=543

Now this is what you need to have in your code. This chip defaults to 4 Mhz

@ __config _CONFIG1, _INTRC_OSC_NOCLKOUT & _WDT_ON & _MCLRE_OFF & _LVP_OFF & _CP_OFF

DEFINE OSC 4

[lockjawz]

I'm using the 16F887 pic chip and I'm using interrupts for multiplexing. I'm trying to get correct timing for pauses by using a FOR loop, but every time the program does an interrupt, it has a 2500uS pause each time. Is there a way to get the timining to one second?

[mackrackit]

You will need to show us your code so we can help you figure out what you are doing wrong.

[lockjawz]

digit1 var portd.0
digit2 var portd.1
digit3 var portd.2
digit4 var portd.3
digit5 var portd.4
digit6 var portd.5
cnt var word
digit var byte
pattern var byte
i var word
first var byte
second var byte
third var byte
fourth var byte
fifth var byte
sixth var byte
seconds var byte
mins var byte
hour var byte
ampm var portb.7


seconds=45
mins=59
hour=11
cnt=0

INTCON=%10100000
OPTION_REG=%00000000
TMR0=6
on interrupt goto isr
INTCON=%10100000

trisa=0
trisd=0
trisb=0
trisc=1
ampm=1


loopa:
button portc.3,1,255,1,i,0,loopa
if portc.3=1 then
seconds=seconds+1
endif
if seconds>59 then
seconds=0
mins=mins+1
endif
if mins>59 then
mins=0
hour=hour+1
endif
if hour>11 then
hour=1
ampm=0
endif
goto loopa

disable
isr:TMR0=6
digit=hour dig 1
lookup digit,[$3F,$06,$5B,$4F,$66,$6D,$7D,$07,$7F,$6F],pattern
porta=pattern
digit6=1
pauseus 500
digit6=0

digit=hour dig 0
lookup digit,[$3F,$06,$5B,$4F,$66,$6D,$7D,$07,$7F,$6F],pattern
porta=pattern
digit5=1
pauseus 500
digit5=0

digit=mins dig 1
lookup digit,[$3F,$06,$5B,$4F,$66,$6D,$7D,$07,$7F,$6F],pattern
porta=pattern
digit4=1
pauseus 500
digit4=0

digit=mins dig 0
lookup digit,[$3F,$06,$5B,$4F,$66,$6D,$7D,$07,$7F,$6F],pattern
porta=pattern
digit3=1
pauseus 500
digit3=0

digit=seconds dig 1
lookup digit,[$3F,$06,$5B,$4F,$66,$6D,$7D,$07,$7F,$6F],pattern
porta=pattern
digit2=1
pauseus 500
digit2=0

digit=seconds dig 0
lookup digit,[$3F,$06,$5B,$4F,$66,$6D,$7D,$07,$7F,$6F],pattern
porta=pattern
digit1=1
pauseus 500
digit1=0
intcon.2=0
resume
enable


end

[mackrackit]

A few things to note.
ON INTERRUPT will not give "true" interrupts. What happens is the code will wait till something like a PAUSE XX is finished before going to the ISR. Many time ON INTERRUPT is good enough, as long as the timing is not "super" critical. ASM interrupts will give true results but hard to setup at times. When you get a handle on this you will want to look at DT's Instant Interrupts. Pretty easy to setup and will give you "TRUE" interrupts.

No matter what method you use you will want the ISR to be as short as possible.

Now for something that might help you...
This is a very useful program
http://www.picbasic.co.uk/forum/content.php?r=159-New-PIC-Utility.-PICMultiCalc

Now look at Timer 1, I think this will work the best in your case. It is a 16 bit timer.
Set the pre-scaler to 1:16 and pre-load to 3036 and you should have very close to a 1 Hz interrupt.