  The control systems of all neutron scattering instruments implemented by the
J\"ulich Centre for Neutron Science (JCNS) are based on Siemens PLC technology.
Historically PROFIBUS has been used for the communication of PLCs with
supervisory computers, decentral periphery systems and other PLCs. Today,
PROFINET IO is the most commonly used industrial real time Ethernet system and
naturally supported by Siemens PLC systems. As a consequence, all new neutron
instruments of JCNS are based on PROFINET IO. For the interfacing to
supervisory computers based on CompactPCI, a CompactPCI carrier board for
PC/104-Plus mezzanines has been developed, allowing the transparent use of the
Siemens PC/104-Plus PROFINET IO controller CP1604 in CompactPCI systems. Linux
is used as the operating system for supervisory computers and the software
development employs the PROFINET IO-Base-API, commonly supported by Siemens
PROFINET IO controllers. On top of this API, an application protocol for the
communication with PLC-based motion systems has been implemented.
