Issue link: https://iconnect007.uberflip.com/i/1216587
54 SMT007 MAGAZINE I MARCH 2020 Because of accessibility, originality, and secu- rity, SEMI is looking at "distributed ledger technologies" (blockchain) as a possible tech- nology to include in their general equipment model (GEM-E30) protocol. As explained in the HP Journal article [3] : "SECS I incorporates the use of RS-232-C cabling and pin definitions and a relatively simple line protocol. SECS II defines larger messages (up to 4.3 Gb) to request and send status information, transfer recipe data, report alarm conditions, send remote equipment control commands, and han- dle a material transfer. SECS I uses a sim- ple ENQ-ACK handshake across an RS232- C line with checksums at the end of each message. SECS I also defines time-out inter- vals between handshake responses, indi- vidual message characters, and message responses. Message headers are defined in SECS I to include equipment identifiers, message identifiers, message block num- bers, and other system information." "SECS II defines message types, format, content, and directions. SECS streams are groups of messages assigned to a general set of equipment functionality. Within each stream, the individual messages are assigned function numbers. For example, SECS stream 1 function 5 (abbreviated S1 F5) is a formatted equipment status request, and stream 1 function 6 is the reply with the status information. Similarly, stream 7 function 5 is used to request the transfer of a process recipe, and stream 7 function 6 is used to transfer the recipe. SECS II also defines whether a reply is required or not, the message content and format (including data item definition headers), and whether a message may be used from equipment-to- host and/or host-to-equipment." The GEM/SECS-II standards are protocol independent. Today, there are two protocols defined by SEMI: SECS-I (E4) for serial com- munication and HSMS (E37) for network com- munication. Most systems today are using the Figure 4: The architecture for Siemens' IoT implementation of OML. (Source: Siemens)