[Etherlab-users] User mode "Register" access methods

[Richard Hacker]

I have never needed `ec_reg*()`, so I have no experience in using them.

Why are you after these functions? They are only used for debugging
during development and for that purpose you have the `ethercat reg_*`
commands.


On Wed, 2026-04-22 at 17:03 +0000, Moebius, Volker wrote:
> Hi Richard,
> 
> thank you for your quick response!
> 
> The functions `ecrt_reg_request_read` and  `ecrt_reg_request_write`
> are documented as
> 
> _This method is meant to be called in realtime context (after master
> activation)_
> 
> Don't they work before the master isn't activated? The `reg_*`
> methods of the CLI seem to work independently from the master
> activation!?
> 
> > -----Original Message-----
> > From: Richard Hacker <ha at igh.de>
> > Sent: Wednesday, April 22, 2026 4:31 PM
> > To: Moebius, Volker <Volker.Moebius at baader.com>; etherlab-
> > users at etherlab.org
> > Subject: Re: [Etherlab-users] User mode "Register" access methods
> > 
> > The 'ecrt_reg_*' family of functions in the C-API mirror the
> > 'reg_*'
> > functions of the CLI tool.
> > 
> > The ESC registers are reserved for the master. As an EtherCAT user,
> > you do not
> > need to touch them.
> > 
> > 
> > 
> > On Wed, 2026-04-22 at 14:16 +0000, Moebius, Volker wrote:
> > > 
> > > 
> > > 
> > > Hello everyone,
> > > 
> > > The `ethercat` CLI tool implements the "Register Access"
> > > functions
> > > `reg_read` and `reg_write`. These functions are using
> > > EC_IOCTL_SLAVE_REG_READ and EC_IOCTL_SLAVE_REG_WRITE to execute
> > these
> > > methods. (lines 433ff of tool/MasterDevice.cpp)
> > > 
> > > Is there a reason why possibly corresponding methods for
> > > "Register
> > > Read" and "Register Write" aren't implemented in the "normal"
> > > user
> > > mode C API (include/ecrt.h)? Don't these methods make sense for
> > > controlling EtherCAT slaves?
> > > 
> > > I'm unfortunately not an EtherCAT expert and I'm confused about
> > > the
> > > different data objects and communication objects. Are the
> > > functions
> > > `ecrt_slave_config_create_reg_request`, `ecrt_reg_request_data`,
> > > `ecrt_reg_request_state`, `ecrt_reg_request_write` and
> > > `ecrt_reg_request_read` related to the same "Register Access"
> > > ("Slave
> > > Registers") as implemented by the CLI? Or do they manage a
> > > different
> > > kind of registers?
> > > 
> > > .
> > 
> > --
> > Mit freundlichem Gruß / Best regards,
> > Richard Hacker
> > --
> > -------------------------------------------------------------------
> > ----
> > Richard Hacker, M.Sc.
> > Entwicklungsingenieur / Development Engineer ha at igh.de
> > 
> > Tel.: +49 201 / 36014-16
> > 
> > Ingenieurgemeinschaft IgH Gesellschaft für Ingenieurleistungen mbH
> > Nordsternstraße 66
> > D-45329 Essen
> > 
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> > ----
> 
> .

-- 
Mit freundlichem Gruß / Best regards,
Richard Hacker
--  
-----------------------------------------------------------------------
Richard Hacker, M.Sc.
Entwicklungsingenieur / Development Engineer
ha at igh.de

Tel.: +49 201 / 36014-16

Ingenieurgemeinschaft IgH Gesellschaft für Ingenieurleistungen mbH
Nordsternstraße 66
D-45329 Essen

https://igh.de | https://etherlab.org

Amtsgericht Essen HRB 11500 | USt-Id.-Nr.: DE 174 626 722
Geschäftsführung:
Frederik Becker, Dr.-Ing. Siegfried Rotthäuser, Jost Braukmann
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