SunSpec Model 10 — Communication Interface Header
SunSpec Model 10 is the Communication Interface Header defined by the SunSpec Alliance, a protocol-level block present on SunSpec-compliant DER devices such as inverters, energy meters, and battery storage systems. The template reads the interface identifier, block length, and interface type via Modbus TCP using function code 3, and exposes the operational status of the physical communication port. The writable control register (ctl) allows enabling or disabling the interface remotely. Importing this SunSpec Model 10 template into ModbusCloud gives integrators a structured view of communication layer health across multi-device sites.
- Protocol
- Modbus TCP
- Connection
- Ethernet, Modbus TCP
- Registers
- 5, read and write
- Brand
- SunSpec
- Last updated
Registers (5)
5 read, 1 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| id | Read | ||||
| l | Read | ||||
| st | Read | ||||
| ctl | Read and write | ||||
| typ | Read |
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If a device is not in the library yet, we build the template for free as soon as we have the register data.
Use cases
- Monitor the communication interface status register to detect when a DER device port goes offline unexpectedly.
- Verify the interface type register on commissioning to confirm RS485 or Ethernet is configured as intended.
- Track the model block length register over time to detect firmware changes that alter the interface descriptor.
- Alert on a status change in the st register to trigger maintenance dispatch before data gaps occur.
- Compare interface type values across multiple site devices to verify consistent communication configuration.
Installation
Ensure Modbus TCP is active on the target SunSpec device by navigating to the communication or Modbus section of the device web interface and confirming TCP is enabled on port 502.
Connect the device to the same LAN segment as the ModbusCloud Gateway, verify IP reachability with a ping test, and note the device IP address and unit ID.
In the ModbusCloud portal, add the Gateway, import the SunSpec Model 10 template, and assign the correct unit ID and base register offset matching the device's SunSpec map start address.
Perform a spot-check by reading the id register: it must return the value 10, confirming the model block is correctly addressed and the Gateway is polling the right register offset.
Things to watch for
The id register returns an unexpected value. What is wrong?
The base register offset is likely misaligned. SunSpec devices typically place the model map starting at Modbus address 40001 (protocol address 40000). If your device uses a non-standard base, adjust the offset in the portal template settings so address 0 maps to the correct wire address.
All five registers read back zero or NaN. What should I check?
First confirm Modbus TCP is enabled on the device and the port is 502. Then verify the unit ID matches what the device expects. SunSpec values are stored big-endian; if your client swaps byte order, all reads will be corrupt. Ensure the ModbusCloud Gateway is using big-endian word order.
My gateway connects but the st register shows an unexpected state. Why?
The st register reflects the actual runtime state of the physical interface. An unexpected status can indicate that the port is administratively disabled, the cable is not seated, or a firmware-level fault has set the interface to a fault state. Cross-check the device event log for interface errors.
Is it safe to write to the ctl register remotely?
Exercise caution. Writing to the ctl register disables or re-enables the communication interface, which will immediately drop all Modbus connectivity on that port, including the polling connection itself. Test writes only during a scheduled maintenance window, and confirm you have an alternative access path to restore the setting if needed.
Knowledge base articles for this device
SunSpec Modbus: one register map for many inverters
SunSpec Modbus is the open register map SMA, Fronius, SolarEdge and Kostal share. The layout, int+SF vs float, the TCP port per brand and reading a mixed fleet.
Fronius Modbus: read a Symo GEN24 over Modbus TCP
Fronius Modbus explained: enable Modbus TCP on the Symo GEN24 on port 502, choose between int+SF and float, read the right SunSpec registers and scale them correctly. Practical guide for solar installers.
SMA Modbus: reading a Sunny Boy over Modbus TCP (installers)
SMA Modbus explained: enable the Modbus TCP server on port 502, choose between the SMA profile (unit ID 3) and SunSpec (unit ID 126), read the right registers, and handle the NaN values at night. Practical guide for installers.
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