IEC 61784-3-3:2010(E) specifies a safety communication layer (services and protocol) based on CPF 3 of IEC 61784-1, IEC 61784-2 (CP 3/1, CP 3/2, CP 3/4, CP 3/5 and CP 3/6) and IEC 61158 Types 3 and 10. It identifies the principles for functional safety communications defined in IEC 61784-3 that are relevant for this safety communication layer. This second edition cancels and replaces the first edition published in 2007. This edition constitutes a technical revision. The main changes with respect to the previous edition are: - updates in relation with changes in IEC 61784-3; - introduction of a secondary watchdog timer (F_WD_Time_2) to cover the use cases 'c