SunSpec Model 15 — Interface Counters Model
SunSpec Model 15 is the Interface Counters Model, a standard SunSpec information model that exposes packet-level traffic statistics for a communications interface on any SunSpec-compliant DER device. Using Modbus TCP, this template reads total inbound and outbound packet counts, broken down into unicast, non-unicast, discard, error, and unknown-protocol sub-counters. A single writable register lets you reset all counters on demand. Installers and integrators use this data in the ModbusCloud portal to monitor communications health, detect packet loss, and diagnose protocol errors on inverters, gateways, and other SunSpec devices.
- Protocol
- Modbus TCP
- Connection
- Ethernet, Modbus TCP
- Registers
- 14, read and write
- Brand
- SunSpec
- Last updated
Registers (14)
14 read, 1 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| id | Read | ||||
| l | Read | ||||
| clr | Read and write | ||||
| incnt | count | Read | |||
| inuccnt | count | Read | |||
| innuccnt | count | Read | |||
| indsccnt | count | Read | |||
| inerrcnt | count | Read | |||
| inunkcnt | count | Read | |||
| outcnt | count | Read | |||
| outuccnt | count | Read | |||
| outnuccnt | count | Read | |||
| outdsccnt | count | Read | |||
| outerrcnt | count | 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 inbound error and discard counters over time to detect a degrading Modbus TCP link before it causes data gaps.
- Compare unicast versus non-unicast inbound packet counts to verify the device is only receiving targeted traffic.
- Track outbound error counts on inverter gateways to identify network congestion or mismatched MTU settings.
- Alert on a rising inbound unknown-protocol counter to spot unauthorised or misconfigured devices on the same segment.
- Reset counters after a maintenance window and verify all counts remain near zero to confirm a clean interface state.
Installation
Enable Modbus TCP on the target SunSpec device through its web interface or commissioning tool, typically found under the communication or network settings section.
Connect the SunSpec device to the same LAN segment as the ModbusCloud Gateway, ensuring TCP port 502 is reachable and not blocked by a firewall.
In the ModbusCloud portal, add the Gateway, then import the SunSpec Model 15 template and assign the correct unit ID and base address matching your device's SunSpec map offset.
Spot-check the incnt register in the live register view: confirm it increments steadily, confirming the model block is correctly located and polling is active.
Things to watch for
All counter registers return zero permanently. What is wrong?
The model block base address may be misconfigured. SunSpec devices place Model 15 at a dynamic offset determined by scanning from the SunS marker. Verify the base address in the template matches the actual offset reported by a SunSpec scanner, and confirm the device firmware actually implements Model 15.
The gateway connects but counter values never change. Why?
If incnt and outcnt stay at zero despite active traffic, the device may not be incrementing interface counters while idle or may require a minimum firmware version to populate this model. Check the device release notes and confirm the Modbus TCP interface itself is actively receiving poll requests.
Why do I get a Modbus exception when reading the model ID register?
SunSpec models are not at fixed addresses. The id and l registers in this template are relative offsets within the model block. If you poll them at absolute address 0 without first locating the SunS marker and walking the model chain, you will hit an unimplemented address range and receive exception code 2 or 4.
Is it safe to write the clr register during live operation?
Writing to clr resets all 12 counter registers simultaneously. Any monitoring trend data based on cumulative deltas will be invalidated. Only clear counters intentionally, for example after a planned maintenance window, and note the timestamp in your portal records to avoid misinterpreting the resulting counter discontinuity as packet loss.
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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