1.8.7. Drivers in IEC

The instance of an I/O driver written in IEC is created by CODESYS. This instance is created at the moment, a device is added in the graphical configuration, that has a reference to this IEC driver in the device description. In the device description typically the library and the function block with the driver is specified.

The initialization and detection of the devices is typically done in the FB_Init method of the driver FB or a specific init function, that can be specified in the device description too (3S drivers uses mostly the Initialize() method).

For the autodetection, a special static FB can be used in the driver FB, so the detection of all card must be done only once for all driver instance, e.g.:

VAR_STAT
  s_HilscherCardMgr : HilscherCardMgr;
END_VAR

HilscherCardMgr is here a special FB, that detects all cards in its FB_Init method.

The implementation of the interfaces and the access to the I/O-configuration are equivalent for the driver in IEC as it was described in the chapters before for the C/C++-drivers.