Simple LED loop

[Dario]

For some reason the delay_ms does not seem to be working. I have the osc1 pin hooked to a function generator at 4 000 000Hz from 0-5V sin wave. afetr programming, the output pin A0 will pulse on for 600us and off for 200us. Could anyone tell me if there is something wrong with my code or if this is a sign that my programmer or CCS or MPLAB are not working properly. Thanks. Dario
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#include <16F873A.h>
#device adc=8
#fuses NOWDT,HS, NOPUT, NOPROTECT, NODEBUG, BROWNOUT, LVP, NOCPD, NOWRT
#use delay(clock=4000000)

void main()
{

setup_adc_ports(NO_ANALOGS);
setup_adc(ADC_OFF);
setup_spi(FALSE);
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DISABLED,0,1);
setup_comparator(NC_NC_NC_NC);
setup_vref(FALSE);

set_tris_a(0x00);

while(TRUE)
{
output_high(PIN_A0);
delay_ms(1500);
output_low(PIN_A0);
delay_ms(1000);
}
}

[jecottrell]

First suggestion will be to change LVP to NOLVP.

Experts will probably find more....

Good luck,

John

[treitmey]

..
edited... nice catch cmdrdan. ???sin wave???

[cmdrdan]

[Dario]

Changing to a square wave makes no differerence,

thanks for the advice.

[neil]

I was going to reply to this sooner, but got sidetracked...

Don't be misled by a sinewave seeming odd on a digital device. The CLKOUT pin drives the crystal with a (square?) wave to set it into oscillation, but the xtal 'rings' with a sinewave at its fundamental frequency. The xtal's oscillation is fed back into the CLKIN pin, which will be converted to a squarewave internally (probably by a schmitt trigger, I have not looked at the datasheet at this point!) to form the clock source for the pic. So, you have two options ,when specifying a xtal oscillator; you can use a crystal (or resonator) to self oscillate, or feed a logic level waveform into the CLKIN pin from a 'canned oscillator' or a signal generator, or anything you like and ignore the CLKOUT signal from the pic.
Because of the squaring done by the (schmitt?) you can probably feed in any periodic signal within the allowed thresholds and it will work as a reliable clock source.

[asmallri]

Change the HS fuse to XT
_________________
Regards, Andrew

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Home of Ethernet, SD card and Encrypted Serial Bootloaders for PICs!!

[Dario]

Thanks guys,

the NOLVP solution was it!!

Sin wave works fine.

[jecottrell]

YES! Newbie, knucklehead gets one right!


Gloatingly,

John