132 ï Process ImageWAGO-I/O-SYSTEM 750Linux Fieldbus Coupler• ioctl(iFD, IOCTL_CHANGE_UPDATE_SPEED, ulValue)[ulValue from 1-10 is valid]Used to set the polling interval to poll ioctl(iFD, IOCTL_KBUSUPDATE,&ulTmp. The default value is 3. This value can be reduced to 1 in order toachieve the highest possible speed of the application. However, this onlymakes sense with very fast I/O modules and a very small user program.The value can also be increased to 10 if only very slow analog I/Omodules are involved and fast updates of the process image are notdesired.• close(iFD)Closes the KBus driverUsing predefined structures, it is possible to access the input or output processimage byte by byte via the following lines:pstPabIn->uc.Pab[byteNo]pstPabOut->uc.Pab[byteNo]or word by word via the lines:pstPabIn->us.Pab[wordNo]pstPabOut->us.Pab[wordNo]Before the input process image can be analyzed, ioctl(iFD,IOCTL_KBUSUPDATE,...) must be called. After changing the output processimage, it is also required to call ioctl(iFD, IOCTL_KBUSUPDATE,...) inorder to send the new values to the modules.
