SECS-II Message Format

Understanding SEMI E5 SECS-II message structure and data types.

What is SECS-II?

SECS-II (SEMI Equipment Communications Standard 2) defines the message format for communication between host systems and semiconductor manufacturing equipment.

Message Structure

Stream Function (SxFy)
├── Header (10 bytes)
│   ├── Device ID (2 bytes)
│   ├── Stream (1 byte)
│   ├── Function (1 byte)
│   ├── P-Type (1 byte)
│   ├── S-Type (1 byte)
│   └── System Bytes (4 bytes)
└── Data Item(s)

Data Types

| Format Code | Type | Description |

|-------------|------|-------------|

| 00 | L | List |

| 10 | B | Binary |

| 11 | BOOLEAN | Boolean |

| 20 | A | ASCII |

| 21 | J | JIS-8 |

| 30 | I8 | 8-byte integer |

| 31 | I1 | 1-byte integer |

| 32 | I2 | 2-byte integer |

| 34 | I4 | 4-byte integer |

| 40 | F8 | 8-byte float |

| 44 | F4 | 4-byte float |

| 50 | U8 | 8-byte unsigned |

| 51 | U1 | 1-byte unsigned |

| 52 | U2 | 2-byte unsigned |

| 54 | U4 | 4-byte unsigned |

Common Messages

S1F1 - Are You There

S1F1 W
.

S1F13 - Establish Communications

S1F13 W
<L [2]
  <A "MDLN">
  <A "SOFTREV">
>.

S2F41 - Host Command Send

S2F41 W
<L [2]
  <A "RCMD">
  <L [n]
    <L [2]
      <A "CPNAME">
      <A "CPVAL">
    >
  >
>.