Re: Can -- Sampling time point of -- 87.5%

Am Dienstag, 4. Dezember 2012, 22:54:12 schrieb John Dammeyer:
> Hi John,
> 
> You need to get your head around the method that a CAN bit is organized.
> It's simple math really.  If a bit is divided into 16 segments use your
> calculator to get the result of  at sample point at segment 14;  14/16.
> 
> John Dammeyer
> 

or more generic
sp  = sample point (in % of the bit time)
ntq = number of time quanta a bit time is built of

sp = ((ntq - phase2segment) / ntq) * 100 


most of the CAN controllers specify at least the last segment in the bit time,
phase2, separately.


 Heinz

> 
> "ELS! The Solution"
> Automation Artisans Inc.
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> 
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of John
> cliffer
> Sent: Tuesday, December 04, 2012 9:48 PM
> To: CANLIST
> Subject: [CANLIST] Can -- Sampling time point of -- 87.5%
> 
> 
> But still it tell's about how to calculate all the segments of an bit
> ......  but not what will be sample rate for this calculation as shown in
> examples.
> 
> 
> Can open standard say try to achieve about  87.5% sample rate for
> acceptable performance on CAN bus.
> 
> Any suggestion for this ?
> 
> 
> 
> //John
> 
> 
> 
> On Wed, Dec 5, 2012 at 3:40 AM, YAP <[email protected]> wrote:
> 
> On Tue, Dec 4, 2012 at 8:29 PM, John cliffer <[email protected]> wrote:
> > Hi,
> > 
> > I am going through this good application note from philips AN1798.pdf.
> > 
> >>> 4.1 Step-by-Step Calculation of Bit Timing Parameters
> > 
> > Here no where it is mentioned about achieving correct sampling time
> 
> point.
> 
> > Canopen suggest to use 87.5% sampling point
> > 
> > 1> How shall we start the calculation of time quanta for segments to
> 
> achieve
> 
> > -- 87.5% sampling time point?
> > 2> What is the formula to calculate sample rate of bit ?
> > 
> > Please suggest.
> > 
> > //John
> 
> IMO good paper here
> http://ww1.microchip.com/downloads/en/AppNotes/00754.pdf
> 
> 
> /Ake
> 
> --
>  ---
> Ake Hedman
> eurosource, http://www.eurosource.se
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