Alias Level
The link between Hardware and Application Level is established with the help of the Alias Level. Each safety module is represented by a so-called alias device, containing all safety-relevant information for the successful configuration and use within the safety loop. The Alias Devices can be found within the safety project shown in the following Figure.
When a new safety project is created, the first alias device "ErrorAcknowledgement.sds" is already created. Based on the icon of the alias device, the type can be determined. The color grey is an indicator for a standard in- or output. Safety yellow is used for safety alias devices. On the left bottom of each icon, a subitem can be found indicating the direction of an alias device. Like in the usual TwinCAT environment, yellow is used here to indicate an input, red for an output. In the case, that an alias device has more than 1 in- or output channel, a black number in the upper right corner indicates the number of channels.