Searching \ for 'RS-422, proto-talk' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/index.htm?key=422+proto+talk
Search entire site for: 'RS-422, proto-talk'.

Truncated match.
PICList Thread
'RS-422, proto-talk'
1996\04\26@022526 by Edwin Baaij

flavicon
face
Bill,

>......  It is posible to manually type in the commands.
>If you are watching what comes over the line, you can understand it.

Absolutly true. But how about the little ram-space in a PIC, let's say a
16C71. If you send a command in text, even if it's a little one, I don't
think you have enough ram to store it before decoding?? And I hope I'm wrong....

> Having a message length field is great, but
>if the receiver gets thaoses bytes garbled, then he may think the message
>is an extremly large one, and spend our lifetime just receiving the
>"last message".

Thrue, I would expect the same happing if the end-mark is garbled? Maybe
putting in an extra checksum for the header data??? ;-)

>Does the slave request at what intervals he wants to be polled?
Yeah, that's the idea. It does it's request when acknowledging a command. I
mine opinion, a slave should never start to talk when not adressed.

I do agree that the slave can't trow away VITAL data if it doesn't know
wheter the master has received it. So the master has to acknowledge this
reception. This ackowledge can also be the request for the next data-packet
or a request for resend (STATUS BYTE 2, bit2=1) when transferring an array.

>The network I have described does not handle vital information.  If
>something goes wrong, then the one or more logs are lost and the
>daily report of the loged data has a glitch.  If people's lives or
>money were involved, then much more would need to be done to insure
>safety.

Can't agree more with you.

An other question. Multi-master mode. I'm a little bit confused about this
term. I would expect that this is a situation where a number of slaves are
being controlled by more than 1 master (why?). Or are we speaking about this
mode because a slave becomes a master when it's talking???

Edwin
Edwin Baaij  (Electronic Engineer)
*********************************************************************
University of Amsterdam                 phone:  +31-20-5256346
Van der Waals,- ZeemanInstitute         fax:    +31-20-5255877
Valckenierstraat 65-67                  e-mail: spam_OUTbaaijTakeThisOuTspamphys.uva.nl
1018 XE Amsterdam
*********************************************************************

1996\04\26@083059 by Bill Cornutt

flavicon
face
----------

Edwin,

>Absolutly true. But how about the little ram-space in a PIC, let's say a
>16C71. If you send a command in text, even if it's a little one, I don't
>think you have enough ram to store it before decoding?? And I hope I'm
wrong....

I have been programming the 6502 for a long time and the PIC for a very
short time.  So it is easy for me to forget that the PIC needs a
diferent concept of programming.  It is very bit orentated.  So you
are right, a text protocal would be impractical on a PIC.


>An other question. Multi-master mode. I'm a little bit confused about this
>term. I would expect that this is a situation where a number of slaves are
>being controlled by more than 1 master (why?). Or are we speaking about this
>mode because a slave becomes a master when it's talking???

I have a situation that redefines the relationship between master/slave.
The master sends out a time of day packet every so often.  The slaves
correct their time of day (if they have been powered down and unable
to count interupt cycles) using this time packet.  It is possible for
the master to be off line and not sending time packets.  If the slaves
don't get a time packet within a certain amount of time, they start
negoattion the time amoung themselves by sending out their own time
packets.  And the results is that all the times that are bad are set
to the same time as the slave with the best time.  So as long as
all the slaves don't get powered down at the same time, they keep good
time without the master.  This is a case of a slave temporary taking
control as a master while the main master is gone.

  ---------
  Bill Cornutt
  .....billcornKILLspamspam@spam@infoserv.com
  Located in Ione California USA.
  A small town in Northern California.
  Sitting against the foothills of the Mother Lode.
  ----------------------------------------------------

1996\04\26@084741 by Roger Books

flavicon
face
>  > Having a message length field is great, but
>  >if the receiver gets thaoses bytes garbled, then he may think the message
>  >is an extremly large one, and spend our lifetime just receiving the
>  >"last message".
>
>  Thrue, I would expect the same happing if the end-mark is garbled? Maybe
>  putting in an extra checksum for the header data??? ;-)

What about just using fixed length buffers?  If you need more data than
one buffer can contain do the obvious.

Roger

More... (looser matching)
- Last day of these posts
- In 1996 , 1997 only
- Today
- New search...