http://www.piclist.com/techref/microchip/math/bit/setbit.htm

http://www.piclist.com/techref/microchip/pwm.htm

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James.
 
 

> -----Original Message-----
> From: piclist-bounces@mit.edu 
> [mailto:piclist-bounces@mit.edu] On Behalf Of Dave Turner
> Sent: 2005 May 26, Thu 10:54
> To: Microcontroller discussion list - Public.
> Subject: [PIC] Indirect file registers, 8 pin software pwm
> 
> Hi again guys,
> 
> I am currently working on a software PWM.  I got it to work fine with
> 1 pin, and now I'm extending it to 8 pins.  I am using a 
> regularly incremented PWMtimer, and 8 GPRs, called PWMlevel 1 
> to 8.  Inside the PWMupdate function, I use a loop, and 
> indirect addressing to access each pwmlevel, and check if 
> it's higher or lower than pwmtimer, to decide when to turn it 
> off.  Therefore, the pwmlevel decides on average, how high the pin is.
> 
> All the loop code works just fine, in checking each pwmlevel, 
> but then I come to set or clear each bit on portb.  I need a 
> way to set or clear a particular bit, depending on a 
> variable, i.e. if the variable is 4, I want to set/clear bit 
> 4.  I cannot think of a way to access a bit, specified on the 
> fly.  The only method I could think of is to use the variable 
> as a loop counter, and in each loop, bit shift d'1' to the 
> left, and then move this to portb.  Unfortunately, this would 
> disturb all the other bits in porta.
> 
> Thanks in advance.
> 
> -- 
> 
> Dave
> All us base are belong to you.
> 
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