Modbus TCP
SunSpec Model 7 — Secure Write Response Model (DRAFT 1)
SunSpec
Overview
SunSpec Model 7 — Secure Write Response Model (DRAFT 1) is a protocol-layer model defined by the SunSpec Alliance for Modbus TCP. It does not represent a physical energy device but provides the response block a DER device populates after processing an authenticated write command. The template reads the request sequence echo, status code, response timestamp, millisecond sub-timestamp, response sequence number, alarm bitfield, and cryptographic algorithm identifier. The single writable register configures the response entry count. Integrators use this model to verify that secure write operations on SunSpec-compliant inverters, meters, or storage systems completed correctly.
Use cases
- Verify that authenticated write commands issued to SunSpec-compliant DER devices completed without errors.
- Monitor the alarm bitfield after each secure write to detect integrity or security alert conditions promptly.
- Track response sequence numbers over time to confirm no write commands were silently dropped or duplicated.
