AS-Interface Safety at Work - System description

AS-Interface has become the standard for binary units in automation. Due to standardisation to IEC 62026-2 and its easy handling this system has established itself worldwide. So far the only signals still conventionally wired have been the safety-related signals. With the AS-i extension "Safety at Work" this has now come to an end. Safety at Work reaches the highest performance level e according to EN 13849-1 (IEC 61508/SIL 3) and can therefore even be used for e-stop applications with the stop category 0 or 1. Approvals for the safe data transmission have been obtained from BIA and TÜV. AS-i Safety at Work can be used for new installations and for retrofitting of existing AS-i installations because it works with all existing masters. Only when repeaters are used it must be ensured that max. one repeater may be used.

The ordinary AS-i 4-bit protocol is a prerequisite for the use of Safety at Work components. As standard masters and controllers are to be used, a safety protocol is generated by the safe slaves and monitored by a new AS-i component, the safety monitor. Each safe slave has a 8 x 4-bit code table which is as individual as a fingerprint. This ensures that each safe slave transmits a different code. This code is inserted into the normal data message during the 8 AS-i cycles (see figure "Safe code sequence in the AS-i message").