Re: H8/3867 Synchronous Uart False Clocks...

From: Paul Carpenter (paul$_at_pcserv.demon.co.uk)
Date: 06/29/04 

Date: Tue, 29 Jun 2004 21:24:43 +0000 (UTC)

On Tuesday, in article
     <40e15232$0$22499$7b0f0fd3@mistral.news.newnet.co.uk>
     phackney@hanoverdisplays.com "Paul Hackney" wrote:

Plenty of experience with asynchronous on H8 (see sig)

>Does anybody know how to reset an H8 /3867 synchronous
>uart when it is part way through receiving a data byte?
>I have tried toggling the RE bit, apparently to no avail.

Why do it that way?

How can you be sure that the time between toggling off and on again
will ensure that no more data bits will be received?

You do of course do at least two read cycles to clear all the receive
buffers as well.

>I believe that noise may be causing a false clock so that
>the uart clocks in the first bit. Some period later, the

Alternativeley you reenabled BEFORE the last data bits have passed.

>real data is sent and the uart will raise RDRF after 7 bits
>have been received. One protection against this would be

Which is what synchronous mode is supposed to do, raise RDRF after
8 bits of data.

>to reset the uart when expecting data. There is no obvious
>way that I can see to do this, except by toggling RE, but
>this appears not to work. Does anyone know if toggling
>RE does indeed reset the receiver? I guess there must be

Normally RE just enables/disables the receiver, it does NOT reset
the receiver.

Even in asynchronous mode when enabling the receiver it is always
advisable to discard the first at least two bytes received as there
may have been data on the receive line which will give scrambled results.

>some kind of FSA which returns to its initial state after
>8 clocks. Is there any other way to persuade it to reset?

Why do you need to reset the receiver at all?

The simpler method is discard known garbage data, as you must be using
some form of synchronisation process with the data.

Monitor the I/O pin for a known idle period before enabling the
receiver. Once you have valid bytes being received just leave the
receiver enabled. 

-- 
Paul Carpenter		| paul@pcserv.demon.co.uk
<http://www.pcserv.demon.co.uk/>        Main Site
<http://www.gnuh8.org.uk/>              GNU H8 & mailing list info.
<http://www.badweb.org.uk/>             For those web sites you hate.

Relevant Pages

  • Re: H8/3867 Synchronous Uart False Clocks...
    ... An attempt to reset the uart, ... Why do I need to reset the receiver? ... >>I have tried toggling the RE bit, ...
    (comp.arch.embedded)
  • Re: Why would an optical mouse suddenly not work?
    ... Bought more batteries today and tried those, ... I've tried the reset ... and two entries for HID compliant keyboard. ... think) uses the same receiver as the mouse. ...
    (microsoft.public.windowsxp.help_and_support)
  • Re: GPSMAP 76 and WAAS
    ... "Menu + power on" is not what I would call a full reset. ... The receiver settings should be back to ... Have you called Garmin? ...
    (sci.geo.satellite-nav)
  • Re: screen saver not working
    ... don't know which one did the trick. ... One thing I did was change the USB port ... thing I did was change the channel on the receiver. ... was reset the mouse. ...
    (microsoft.public.windowsxp.general)
  • Re: 1-32 Khz in 1khz divisions
    ... >>>The initial two clocks during reset DOES cause some heartburn. ... >>>devise a nice receiver that lights an LED. ... >single gate driving the reference shield: ...
    (sci.electronics.design)