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Structure of an openSAFETY frame

openSAFETY duplicates the frame to be transferred and conjoins the two identical frames into one openSAFETY frame. Hence, the openSAFETY frame consists of two subframes with identical content.

Each subframe is provided with an individual checksum as a safeguard. The receiver compares the identical content of the two subframes. The probability that the same data is changed or destroyed in two such subframes is extremely low, and even lower the more the frame length increases. That said, even in this extremely exceptional case, the checksums still serve as a corrective. The special format of openSAFETY frames, i.e. the two subframes with their own individual checksums, also makes “masquerades” extremely unlikely to occur, and precludes any erroneous processing of a masked standard message.

 

The safety frame is contained in the payload data area of a standard frame; it is comprised of two identical subframes, each of which carries an individual checksum to safeguard its integrity