hsms (high-speed secs message services)

HSMS (High-Speed SECS Message Services) is the **TCP/IP-based communication protocol** that replaced the original RS-232 SECS-I serial link for connecting semiconductor equipment to factory host systems. It's defined by SEMI standard E37. **Why HSMS Replaced SECS-I** **Speed**: SECS-I was limited to 9600 baud over serial cables. HSMS runs over Ethernet at **100Mbps to 1Gbps**. **Distance**: Serial cables were limited to about 15 meters. TCP/IP works over any network distance. **Multi-connection**: HSMS supports multiple simultaneous connections while SECS-I was point-to-point only. **Reliability**: TCP/IP provides built-in error detection, retransmission, and flow control. **Connection Modes** **Passive mode** (most common in production): Equipment listens for incoming connections from the host. **Active mode**: Equipment initiates the connection to the host. **Message Types** • **Data Message**: Carries SECS-II messages (the actual process data, alarms, recipes) • **Select Request/Response**: Establishes communication session • **Deselect**: Closes session gracefully • **Linktest**: Heartbeat to verify connection is alive • **Separate**: Force-closes session **Typical Setup** Each tool has a unique IP address and port number. The host (MES/EI) connects to each tool individually. HSMS wraps SECS-II message content—the application-layer protocol (SECS-II) remains the same whether transported over SECS-I or HSMS.