Post by thread:counter won't count above 1F

Mark Willcox wrote: > > Hi all > I'm trying to understand TMR0. The attached code won't count above 1F. > When it reaches 1F the counter resets and counts up to 1F again. I thought > it would count to FF and then reset. Whats wrong with the code? > I copied the code from Introduction to PICS.. The original code used RTCC > instead of TMR0. Could this be the problem? > Thanks in advance, Mark > ________________________________________________________________________ > Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com > > ------------------------------------------------------------------------ > Name: secount.asm > secount.asm Type: ASM File (application/x-unknown-content-type-asm_auto_file) > Encoding: base64 You have used the "p16f84.inc" file, so you don't need to define these... PORTB equ 06 STATUS equ 03 Z equ 02 TMR0 equ 01 This defines 'cntr' at the location for the PCLATH register. cntr equ 0A Use the first general purpose RAM location at 0x0C instead. cntr equ 0Ch For your timing loop, try this, by using the T0IF flag. This is set = 1 when TMR0 overflows from FF - 00. loop btfss INTCON,T0IF ; wait for TMR0 overflow goto loop bcf INTCON,T0IF ; clear flag incf cntr,1 ;increment counter file movf cntr,0 ;mov counter file to W movwf PORTB ;output counter value to PORTB goto loop Depending on your XTAL (RC) speed, you may only see a blur on PORTB. To slow things down a little, try this. TimeL equ 0Dh ; RAM register 0Dh clrf TimeL loop btfss INTCON,T0IF ; wait for TMR0 overflow goto loop bcf INTCON,T0IF ; clear flag decfsz TimeL goto loop incf cntr,1 ;increment counter file movf cntr,0 ;mov counter file to W movwf PORTB ;output counter value to PORTB goto loop If it is still too fast, you may need to add a TimeH register in the loop as well. -- Best regards Tony http://www.picnpoke.com spam_OUTsalesTakeThisOuTpicnpoke.com