Let me try again; There is no 3xxxx addresses in the products. It is a
notation written with text, by people. the first written digit convey the
type. That's it.

Looooong time ago, back when the Modbus came to life it was simply a memory
area that one could read and possibly write. And then documentation
specified what was in each bit/byte/word. And with such approach, it is
probably possible to implement Modbus in less than 100 bytes of very
expensive (E)PROM back then. Not until later was there address validity
checks and what not.

FTR; It is completely beyond me how Modbus became as popular as it has, and
that this happened decades after it was introduced on the market. When I
was part of a startup and we were developing a serial protocol in
1984/1985, we knew of Modbus and thought it was a really poor protocol
(couldn't even do floating point numbers). I don't like it, but just about
every electric thing can be purchased with Modbus option...

Cheers
Niclas

On Wed, Jul 15, 2020 at 9:39 PM Christofer Dutz <christofer.d...@c-ware.de>
wrote:

> Hi Niclas,
>
> Protocol-wise the numbers could be up to 65535 as they use an unsigned 16
> bit integer as an address.
>
> I guess what would be interesting, would be what address is going over the
> wire for "30001" for example.
> Also as a register is always a 16 bit value, the increments by two sort of
> puzzle me.
>
> I think Modbus is an extremely simple protocol but we need to get a
> feeling for it's usages.
>
> It does seem as if the industry tends to wrap some aspects in software
> bubble-wrap ... we gotta find out what's below.
>
> Chris
>
>
> ´╗┐Am 15.07.20, 15:23 schrieb "Niclas Hedhman" <nic...@hedhman.org>:
>
>     It is a common format in equipment documentation. I am currently
> working
>     with an electric meter. See screenshot from its manual;
>
> https://ipfs.subutai.io/ipfs/QmPsra6ExrkSX9GCYWgHa6CTfJbBnddLVXJ3NmJjmAYrAk
>
>     At protocol level, there are no such "high numbers", just that the
> industry
>     got used to write "4" instead "holding register". It is a "people
> thing",
>     not a technical one.
>
>     HTH
>     Niclas
>
>     On Wed, Jul 15, 2020 at 6:11 PM Christofer Dutz <
> christofer.d...@c-ware.de>
>     wrote:
>
>     > Hmmm ...
>     >
>     > Regarding: 10012 being a coil and 4xxxx a register.
>     >
>     > Well the coils and registers are completely different things ...
> They are
>     > accessed via completely different requests.
>     > That might be some sort of convenience convention, but I wouldn't
> call
>     > that a standard (I've actually never seen it before)
>     > Would you then just subtract 40000 from every register or would you
> just
>     > configure registers starting with numbers 40000?
>     >
>     > What do the others think? The address format does reference
> registers ...
>     > should we be doing the translation?
>     >
>     > I guess that the general use-case would be that someone has a look
> at his
>     > Modbus config and says that he wants "Register X"
>     > and not "The Register Y references" (which seems to be one less) ...
> I
>     > might even swing my vote in favor to using register numbers instead
> of
>     > addresses.
>     >
>     > But then I ask myself: How can I address register 0 in ModbusPal ...
> that
>     > would require an address that's impossible to send.
>     >
>     > Chris
>     >
>     >
>     > Am 15.07.20, 11:51 schrieb "Niclas Hedhman" <nic...@hedhman.org>:
>     >
>     >     Personall, I prefer that Register Numbers are used in APIs and
> that the
>     >     address is only seen if you analyze the over-the-wire format,
> but maybe
>     >     that is just me. A big reason for this is that any interface
> presented
>     > to
>     >     an operator would need to use RegNumbers, as most (possibly all)
>     >     documentation of equipment has RegNumbers and some are lacking
> the
>     >     addresses. It is also common that the register type is part of
> the
>     > Register
>     >     Number, such as 10012, where the first 1 indicates "coil"
> (IIRC). and
>     >     holding registers are in 4xxxx. Ideally(!), this is also handled
> by the
>     >     register/address parser.
>     >
>     >     Niclas
>     >
>     >     On Wed, Jul 15, 2020 at 5:43 PM Christofer Dutz <
>     > christofer.d...@c-ware.de>
>     >     wrote:
>     >
>     >     > Hmm .. so are we doing it correctly?
>     >     >
>     >     > I mean Wireshark isn't the ideal reference here as I have
> several
>     > valid
>     >     > packets in the KNX space, where WireShark just says "corrupt
>     > package".
>     >     >
>     >     > So if you enter an "holding-register:42" address it tries to
> read the
>     >     > register number 43 in ModbusPAL.
>     >     >
>     >     > I guess as we are reading an "address" we are correct and
> probably as
>     >     > ModusPAL says register number, that might be correct too?
>     >     >
>     >     > Chris
>     >     >
>     >     >
>     >     > Am 15.07.20, 10:54 schrieb "Niclas Hedhman" <
> nic...@hedhman.org>:
>     >     >
>     >     >     The issue with 1-offset is that the "Register Number"
> found in
>     >     >     documentation is at an "Address" one position less. So Reg
> 41 has
>     >     > Address
>     >     >     40. Som libraries expect Register Numbers and some expect
>     > Register
>     >     > Address.
>     >     >     And every so often, one mixes that up.
>     >     >
>     >     >     On Wed, Jul 15, 2020 at 2:53 PM Christofer Dutz <
>     >     > christofer.d...@c-ware.de>
>     >     >     wrote:
>     >     >
>     >     >     > ....
>     >     >     >
>     >     >     > While looking for more Infos I found out I once wrote a
>     > tutorial
>     >     > page for
>     >     >     > PLC4X __
>     >     >     >
>     >     >     > https://plc4x.apache.org/users/plc4j/virtual-modbus.html
>     >     >     >
>     >     >     > I so totally hate searching the web and getting my
> answers
>     > answered
>     >     > by
>     >     >     > myself.
>     >     >     >
>     >     >     > Chris
>     >     >     >
>     >     >     > Am 15.07.20, 08:31 schrieb "Christofer Dutz" <
>     >     > christofer.d...@c-ware.de>:
>     >     >     >
>     >     >     >     Hi Niclas,
>     >     >     >
>     >     >     >     when preparing a workshop for the Building IoT we
> were
>     > looking
>     >     > for
>     >     >     > something where you could simulate a Modbus Slave.
>     >     >     >     Most of these were Windows only solutions, so
> ModbusPAL
>     > was one
>     >     > of the
>     >     >     > very few solutions that were pure-java.
>     >     >     >
>     >     >     >     Don't quite understand what the thing with the
> offset is
>     > however
>     >     > ...
>     >     >     > should be easy to fix ... I mean if I say address 42 in
> PLC4X,
>     >     > Wireshark
>     >     >     > says 42, but in Modbus Pal I think it has to be 43 ...
> don't
>     > quite
>     >     > get it.
>     >     >     >
>     >     >     >     Chris
>     >     >     >
>     >     >     >
>     >     >     >
>     >     >     >     Am 15.07.20, 03:54 schrieb "Niclas Hedhman" <
>     > nic...@hedhman.org
>     >     > >:
>     >     >     >
>     >     >     >         What is ModbusPAL?
>     >     >     >
>     >     >     >         The 1-offset in Modbus has caused a lot of
> confusion
>     > over the
>     >     >     > years.
>     >     >     >
>     >     >     >         On Tue, Jul 14, 2020 at 11:03 PM Christofer Dutz
> <
>     >     >     > christofer.d...@c-ware.de>
>     >     >     >         wrote:
>     >     >     >
>     >     >     >         > Sorry for the noise ...
>     >     >     >         >
>     >     >     >         > this was a false positive ... the driver was
> doing
>     > things
>     >     >     > correctly.
>     >     >     >         > It seems the ModbusPAL was just off by one ;-)
>     >     >     >         >
>     >     >     >         > Chris
>     >     >     >         >
>     >     >     >         >
>     >     >     >         >
>     >     >     >         > Am 14.07.20, 15:51 schrieb "Christofer Dutz
> (Jira)" <
>     >     >     > j...@apache.org>:
>     >     >     >         >
>     >     >     >         >     Christofer Dutz created PLC4X-214:
>     >     >     >         >     -------------------------------------
>     >     >     >         >
>     >     >     >         >                  Summary: [Modbus] Holding
> register
>     >     > addresses
>     >     >     > have an
>     >     >     >         > offset of 1 (Not reading the correct address)
>     >     >     >         >                      Key: PLC4X-214
>     >     >     >         >                      URL:
>     >     >     > https://issues.apache.org/jira/browse/PLC4X-214
>     >     >     >         >                  Project: Apache PLC4X
>     >     >     >         >               Issue Type: Bug
>     >     >     >         >               Components: Driver-Modbus
>     >     >     >         >         Affects Versions: 0.7.0
>     >     >     >         >                 Reporter: Christofer Dutz
>     >     >     >         >                 Assignee: Christofer Dutz
>     >     >     >         >                  Fix For: 0.8.0
>     >     >     >         >
>     >     >     >         >
>     >     >     >         >     If I set holding the following holding
> registers
>     > to:
>     >     >     >         >
>     >     >     >         >     1000: 41
>     >     >     >         >     1001: 42
>     >     >     >         >     1002: 43
>     >     >     >         >
>     >     >     >         >     And then read: holding-register:1001 ... I
> get
>     > the
>     >     > value 43
>     >     >     > returned.
>     >     >     >         >
>     >     >     >         >
>     >     >     >         >
>     >     >     >         >     --
>     >     >     >         >     This message was sent by Atlassian Jira
>     >     >     >         >     (v8.3.4#803005)
>     >     >     >         >
>     >     >     >         >
>     >     >     >
>     >     >     >
>     >     >     >
>     >     >
>     >     >
>     >
>     >
>
>

Reply via email to