Simple TMR1 application example needed [Archive]

flotulopex

- 3rd February 2010, 19:59

Hello,

I want to count, as an example, how much time (or instruction cycles) a FOR/NEXT loop takes to do its count using TMR1 in Timer mode.

So I made this piece of code but I can never read any result in the PIC's memory (I have the PIC connected to my PICKit2 so I can readout the memory easely).

What am I doing wrong?

<html><head></head><body><pre><code>' Fuses PIC16F88
@ DEVICE INTRC_OSC_NOCLKOUT
@ DEVICE PROTECT_OFF
@ DEVICE WDT_ON
@ DEVICE PWRT_OFF
@ DEVICE MCLR_OFF
@ DEVICE BOD_OFF
@ DEVICE LVP_OFF
@ DEVICE CPD_OFF
@ DEVICE DEBUG_OFF
@ DEVICE CCPMX_OFF
@ DEVICE2 IESO_OFF
@ DEVICE2 FCMEN_OFF

'_________________________________________________ ___________________________
' Registers 76543210
OPTION_REG = %10000000 ' PORTB Pull-Ups disabled
ANSEL = %00000000 ' Disable analog inputs
ADCON0 = %00000000 ' A/D Module is OFF
CMCON = %00000111 ' Comparator Module is OFF
INTCON = %00000000 ' All Interrupts are disabled
TRISA = %00000000 ' Set Input/Output
PORTA = %00000000 ' Ports High/Low
TRISB = %00000000 ' Set Input/Output
PORTB = %00000000 ' Ports High/Low
T1CON = %00000000 ' TMR1 settings

'_________________________________________________ ___________________________
' Variables
Ctr_A VAR BYTE ' counter
Ctr_B VAR WORD ' counter
Mem_Loc VAR WORD ' memory Location Pointer
Result VAR WORD(10) ' holds the TMR1 value

Ctr_A = 0
Ctr_B = 0
Mem_Loc = $FA8
Result = 0

'_________________________________________________ ___________________________
' Program
FOR Ctr_A = 0 TO 9 ' 10 count loop

TMR1H = 0 ' reset Timer
TMR1L = 0 ' reset Timer
T1CON.0 = 1 ' start Timer

FOR Ctr_B = 0 TO 100 : NEXT Ctr_B ' let TMR1 increment a little

T1CON.0 = 0 ' stop Timer
Result.LowByte = TMR1L ' store LOW TMR1's value to Result
Result.HighByte = TMR1H ' store HIGH TMR1's value to Result
Result[Ctr_A] = Ctr_A ' assign Result's index

NEXT Ctr_A ' loop

ERASECODE Mem_Loc ' free-up 32 mem locations

FOR Ctr_A = 0 TO 9 ' 10 count loop
WRITECODE Mem_Loc, Result[Ctr_A] ' store Result(x) var
Mem_Loc = Mem_Loc + 1 ' increment mem location
NEXT Ctr_A ' loop

END</code></pre></body></html>

Darrel Taylor

- 4th February 2010, 08:46

Hi Roger,

It's working..

But the 16F88 defaults to 31.25khz internal oscillator.
So it takes a while to complete.

If you read it back too quick, you don't see anything.

Adding ...
    OSCCON = %01100010 ; Set Internal OSC to 4mhz.
it takes a fraction of a second to complete.

And this line overwrites the Timer results, so you might want to comment it...
Result[Ctr_A] = Ctr_A ' assign Result's index

hth,

Added:
F88's Flash memory is written in blocks of 4, so you'll need to change the length of the data.

flotulopex

- 4th February 2010, 09:52

Thanks Darrel,

After I posted my message, I added a blinky and noticed the "very slow motion".

Now I use a 20MHz crystal so I corrected the configuration fuse and added the DEFINE information.

But new problems come up...

To get the program starting, I need to approach my finger close to the xtal (?!) - it looks like some capacitance issue. I added a 10Mohms resistor in parallel with the xtal and now, the program starts everytime I power the PIC.

On the other hand, my PICKit2 programmer won't recognize my PIC when I have a 20MHz xtal intalled on the breadboard. I don't know what this comes from. Maybe one of you does?