A control unit is described for technical installations, devices and/or
machines having a microprocessor, a programmable memory and a housing
enclosing the microprocessor and programmable memory. Data lines lead out
of the housing for connection with an external device for writing data to
the programmable memory. The control unit is enclosed in the housing such
that the operability of the control unit is at least partly destroyed
when the housing is opened. The control unit furthermore has a check
device that checks for authorization a write access by which data are
written to the programmable memory over the data line, and causes the
data to be written to the programmable memory only in case of a
successful check of authorization.