I try to reach a simple profibus master code ; reads and writes
siemens PLC. can anybody help me ? a documentation a simple code or
someting like that. i m new at profibus.

sagittarius schrieb:

"simple" and "profibus" are mutually exclusive.

Tilmann

--
http://www.autometer.de - Elektronik nach Maß.

On 16 Oct 2006 00:38:04 -0700, "sagittarius" <omur.yavuz@gmail.com>
wrote:

You should really get some background information about Profibus,
before you even start to dream about implementing something with it.

Start for instance with www.profibus.org, but I would really suggest
reading some tutorial book about Profibus, e.g. "The New Rapid Way to
Profibus DP" by Manfred Popp, which at least some have liked.

Siemens PLCs are hard to use and you would definitively need a
configuration tool to do anything useful with it, so you would anyway
need a PC with a Profibus card and some configuration software.

While Profibus-DP (but not Profibus-PA) is simply RS-485 with
asynchronous characters, there are some problems. Most of the speeds
are not standard serial communication speeds, so at least a special
crystal is needed for the baud-rate generator.

The Rx/Tx timing is critical, so the 16550 type family UARTs are
practically useless, since it does not have hardware Rx/Tx RS-485 line
control or even a usable "Tx shift register empty" interrupt instead
of the "Tx data register empty" interrupt found on 16550.

To fully qualify for proper poll cycle timing, most PC type operating
systems (such as Windows or Linux) have far too much latency, so in
practice, all Profibus PCI cards use some kind of ASIC doing the
actual Profibus-DP cyclic polling.

Paul

"sagittarius" <omur.yavuz@gmail.com> wrote in message
news:1160984284.795195.94210@m7g2000cwm.googlegrou ps.com...
It has been a while since I used profibus and industrial controllers in
general, but I remember a couple things. One was that there was no "simple"
profibus.

There's more than one "flavor" or "mode" of profibus, to begin with. Most
(all?) Profibus devices us an ASIC from Siemens to interface with the
profibus.

If all you want to do is read and write the PLC, I think you can do it more
simply through the serial bus and the Modbus protocol, if Siemens supports
it.
This probably isn't available in the smallest PLC'S.

You might try Siemens...

On Mon, 16 Oct 2006 15:47:07 -0400, "Rufus V. Smith"
<nospam@nospam.com> wrote:

While Modbus has been recently available for some Siemens PLCs, the
old Siemens 3964R/RK512 serial protocol should be available for a
large range of PLCs.

Paul