Instant Interrupts - Revisited

[bcd]

I have been playing with the code shown below on a 16f737 as I was trying to get different prescaler values into the int routinues. As part of the testing I stripped the code right back to just be a simple interrupt with a value loaded into the pre-load registrer, but I seem to end up with an interrupt time of 204uS. According to the Timer Calc in Mister E's PicMulti Calc I should get an interrupt every 5.019mS. (see attached image for capture of the output waveform - I love my PICkit 2!)

This code is lifted straight from Darells example with the blinky led (1-2-3 version), and all I have done is add the pre-load. I have also removed the pre-load and still get the same time for the interrupt.

DEFINE OSC 20

rs_led      var portb.7 ' rs232 led
led         var portc.4 ' was Data_Out line

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

INCLUDE "DT_INTS-14.bas"     ' Base Interrupt System
INCLUDE "ReEnterPBP.bas"     ' Include if using PBP interrupts


ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
       INT_Handler   TMR0_INT,  _doBAM,   PBP,  yes
     endm
    INT_CREATE     ; Creates the interrupt processor
ENDASM

OPTION_REG = OPTION_REG & $80 | 1     'Set TMR0 Prescaler to 256, leave RBPU alone

TMR0 =  158 ' preload with 158 to give 21uS interrupts (at 1:1)
' this should then give Interrupt every 5.019mS at 1:256

@ INT_ENABLE  TMR0_INT     ; enable Timer 1 interrupts
'~~~~~~~~~~~~~~~~~~

goto main      ' jump over ISR

'---[TMR0 - interrupt handler]--------------------------------------------------
doBAM:
toggle rs_led
@ INT_RETURN

'~~~~~~~~~~~~~~~~~~~~~~~~~~~
 high rs_led
main:

'''''''''''''''''''''''
' do some flashing led stuff
'''''''''''''''''''''''
high led
pause 500
low led
pause 500
goto main

There has got to be something really simple I am missing...
bill.

[Darrel Taylor]

Use OPTION_REG = %11010111

And load the timer on every interrupt.
<br>

[bcd]

Thanks,

See told you it would be something really simple I missed..

doBAM:
   toggle rs_led
   TMR0 =  158     ' reload the pre-load
   @ INT_RETURN

(Hey Darrel - how do you get your code blocks so colourful and properly indented ?)

bill.

[skimask]

(Hey Darrel - how do you get your code blocks so colourful and properly indented ?)
bill.

http://www.picbasic.co.uk/forum/showthread.php?t=6221

The page may take awhile to load.....

[leisryan]

Hello;
I'm Ryan form the Philippines I must admit DTS-14 ints rules!!! i'd like to know how can i turn the interrupt on and off for USART continues recepton I'm using PIC16f877a toggling register PIE.5 doesn't seem to work

Thanks

PS.

Part of my project i'm paying my tuition continue college again OSY for sometime now hehe (",)

[Archangel]

Check out this post, esp. post 5, http://www.picbasic.co.uk/forum/showthread.php?t=3251

[mister_e]

you can use
@ INT_ENABLE RX_INT

and

@ INT_DISABLE RX_INT