ICSP not recognizing..

[sirvo]

Yeap..

I always erase pic after programming and MCLR is tied like this:

VCC-10K-1N4148-MCLR-VPP(ICSP)

Thanks!!

[mackrackit]

Does it always work the first time?
Try adding capacitors between VDD and VSS. As close as you can to the PIC on both sides. I had a similar problem once with the PICSTART and an 18F'r. ???

[sirvo]

Well, I've tried that too... same thing..

Sometimes it works on the second try... i do not know..

Well, got another problem, could you help again???

I'm trying to make TMR1 interrupt at 36kHz.

It uses a 20Mhz crystal... The code is below:

@ DEVICE pic16F877, HS_OSC ; System Clock Options
@ DEVICE pic16F877, WDT_OFF ; Watchdog Timer
@ DEVICE pic16F877, PWRT_ON ; Power-On Timer
@ DEVICE pic16F877, BOD_OFF ; Brown-Out Detect
@ DEVICE pic16F877, CPD_OFF ; Data Memory Code Protect
@ DEVICE pic16F877, PROTECT_OFF

define OSC 20 

INT       VAR     PIR1.0  ' OVERFLOW flag
START   VAR     T1CON.0 ' START TMR1
LOAD     VAR     word

'------- Configurações iniciais -------------------- 
TRISA  = %00000000 ' PORTA
TRISB  = %00000000 ' PORTB 
TRISC  = %00000000 ' PORTC
TRISD  = %00000000 ' PORTD 
TRISE  = %00000000 ' PORTE 

INTCON = %11000000  ' enable global interrupt
OPTION_REG = %00000000
ADCON1 = %10001111  ' all digital
T1CON = %00000000   ' TMR1 1:1 prescaler
PIE1 = %00000001    ' Henable  TMR1 INT
START = 0
INT = 0
LOAD = 65404 '  INT. 36KHz
'--------------------------------------------------- 
ON INTERRUPT GOTO SINUS

TMR1L = LOAD.lowbyte
TMR1H = LOAD.highbyte
START = 1 
PORTB.0 = 1
MAIN:      
        GOTO MAIN    

 
DISABLE
SINUS:  INT = 0
           TMR1L = LOAD.lowbyte
           TMR1H = LOAD.highbyte
           PORTB.0 = 1 ' JUST TO MEASURE THE FREQ. ON OSCILLOSCOPE
           PORTB.0 = 0
RESUME
ENABLE

end

The oscilloscope do not shows 35.9kHz, but 30~33kHz...

Anything I can do?

Thanks again!

[mister_e]

make sure you also disable the LVP mode. This pin have to be loaded to GND when progaming.


And then... when you reload a 16Bit timer you want to add the reload value instead of just dumping the values in. Finally you want to stop it, then add the reload value, the restart the timer.

Depending how accurate you want it, not a bad idea to switch to Darrel's instant INTs (PBP or ASM... where asm is always handy .. )

[skimask]

Try this and see what happens, should give you a 50% duty cycle ~36khz square wave on your o'scope:

@ DEVICE pic16F877, HS_OSC ; System Clock Options
@ DEVICE pic16F877, WDT_OFF ; Watchdog Timer
@ DEVICE pic16F877, PWRT_ON ; Power-On Timer
@ DEVICE pic16F877, BOD_OFF ; Brown-Out Detect
@ DEVICE pic16F877, CPD_OFF ; Data Memory Code Protect
@ DEVICE pic16F877, PROTECT_OFF
DEFINE OSC 20
load con 65468:intcon=$c0:option_reg=0:adcon1=$87:t1con=1:pie1=1:c var byte
goto main
ON INTERRUPT GOTO SINUS
TMR1L=LOAD.lowbyte:TMR1H=LOAD.highbyte
MAIN:      GOTO MAIN    
DISABLE
SINUS: if pir1.0=1 then
          pir1.0=0:tmr1l=load.lowbyte:tmr1h=load.highbyte:c=c+1:portb.0=c.0
          endif
RESUME
ENABLE
END

And take note of Mr_E's note about adding values.

[sirvo]

Thanks for answering..

I've trie instant interrupts but it stays the same..

I've also tried the code you wrote Skimask... the oscil. shows ~50kHz... The load you typed is too large...

Don't know what is wrong.. The oscilloscope is a Tektronix TDS2014.. it is working ok!

Anything else I can do?

Let me tell you something.. I'm using 22p capacitor at the @20Mhz... is that ok?

[skimask]

I've also tried the code you wrote Skimask... the oscil. shows ~50kHz... The load you typed is too large...

Well then change it!

Or perhaps you wish for me to change the LOAD value myself and re-post the exact same code with that one change so you can cut and paste it over and try it again?

I never said my code would be perfect, but your code had a few faults that needed to be corrected.

[mister_e]

How accurate you want it?

Skimask changed the reload value... hence why you have higher value.

try...

@       __CONFIG _HS_OSC & _WDT_OFF & _LVP_OFF & _PWRTE_ON & _BODEN_ON

define OSC 20 

INT       VAR     PIR1.0  ' OVERFLOW flag
START   VAR     T1CON.0 ' START TMR1
LOAD     VAR     word

'------- Configurações iniciais -------------------- 
TRISA  = %00000000 ' PORTA
TRISB  = %00000000 ' PORTB 
TRISC  = %00000000 ' PORTC
TRISD  = %00000000 ' PORTD 
TRISE  = %00000000 ' PORTE 



OPTION_REG = %00000000
ADCON1 = %10001111  ' all digital
T1CON = %00000000   ' TMR1 1:1 prescaler
PIE1 = %00000001    ' Henable  TMR1 INT
START = 0
INT = 0
LOAD = 65404 '  INT. 36KHz
@TIMER1=TMR1L
TIMER1  var word EXT

'--------------------------------------------------- 
ON INTERRUPT GOTO SINUS

TIMER1=LOAD
INTCON = %11000000  ' enable global interrupt
START = 1 
PORTB.0 = 1
MAIN:      
        GOTO MAIN    

 
DISABLE
SINUS:  
           @ MOVE?CT 0, T1CON, TMR1ON
           TIMER1=TIMER1+LOAD
           @ MOVE?CT 1, T1CON, TMR1ON                       
           toggle PORTB.0
           INT = 0
RESUME
ENABLE

end

you should have something like 18KHz signal.. so yeah, your interrupt is still 36Khz... i just toggle the pin..

I tend to stay away of ON INTERRUPT when i need accuracy. ASM is the best while DT INST with PBP is still good enough for many purpose.