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Introduction to SECS/GEM - Beginner's Guide - Introduction to SEMI E5 SECS-II Message

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Introduction to SECS/GEM - Beginner's Guide
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SEMI E5 SECS-II Message

As described in the article's introduction section, this standard provides the APIs for interfacing between Host and Equipment. In this standard, each message is represented in Function and grouped in Stream (category).

Like Webservice, each SECS-II message consist of Header (which typically contains the method/function name, transaction type=request/reply) and Body (which specify the parameter's name and type). In some functions, the Body may be empty.

Below describes the convention of the SECS-II Message Structure

Message Header

Fn Identifier Fn Name/Description Message Block Message Direction Need Reply
Sn,Fm Name of Function (XXX)

S,M

H->E

H<-E

H<->E

reply (required)

"blank" (no reply required)

Where:

  • Sn = Stream n
  • Fm = Function m. Odd function number denotes Primary message (request) while even function number (SnFm+1) denotes the Secondary/Reply message
  • (XXX) = Short mnemonic
  • S,M = S=Single, M=Multi-block
  • H,E = H=Host, E=Equipment

Description

A description of the action generated by the function.

Structure

The function's message body. Detailed structure showing lists and defined items. Lists are denoted by a capital L followed by the length seprated by a comma. The individual elements in the list are numbered on seprate lines.

Nested lists are indented to emphasize the structure. The detailed form of the items is given in the define section at the beginning of the transaction. The symbols "<" and ">" are used to item header. A detailed description of each data item as well as a list of the allowable data formats can be found in the Data Item Dictionary

Exception:

Special cases in the structure that have a different meaning. 
Sn,Fm+1 Name of function (same structure as above (secondary) except never with reply)