# tt_eth_firmware_signature

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## Name

### Prometheus Metric Name

```
tt_eth_firmware_signature
```

### Metric Path (tt-telemetry)

Schema:

```
{hostname}/tray{tray}/chip{chip}/channel{channel}/tt_eth_firmware_signature
```

Example path:

```
bh-glx-c09u02/tray1/chip2/channel0/tt_eth_firmware_signature
```

## Description

The 16-bit ERISC firmware signature for a specific Ethernet channel, read directly from the heartbeat word in the Ethernet core's L1 memory.

The heartbeat word is a 32-bit value: the upper 16 bits carry a signature identifying which firmware is running on the core, and the lower 16 bits are a counter the firmware increments while alive. This metric reports the signature half only (already shifted into the low 16 bits of the reported value). The companion metric [`tt_ethernet_heartbeat`](tt_ethernet_heartbeat.md) reports whether the counter half is advancing.

The heartbeat word is read from:
- **Wormhole B0:** `ETH_HEARTBEAT_ADDR` (0x1C) in the Ethernet core's L1.
- **Blackhole:** the `heartbeat[0]` field of the `eth_status_t` struct inside `BOOT_RESULTS_ADDR` (0x7CC70).

The layout is identical on both architectures.

This metric is collected unconditionally on every Ethernet core; no ARC telemetry or topology information is required to populate it.

### Observed values

| Signature | Meaning |
|---|---|
| `0xABCD` (43981) | Base ERISC firmware is running on the core. |
| `0xDCBA` (56506) | AERISC software fabric has taken over the core. See `aerisc_context_switch` in `tt_metal/hw/inc/internal/tt-1xx/blackhole/eth_fw_api.h`, which writes `0xdcba0000 \| counter` into the heartbeat word to mark "software has taken over." This is the authoritative indicator that the fabric firmware is the one driving the core. |
| Other | A firmware variant not enumerated here, an uninitialized/corrupt heartbeat word, or a core that is not running ERISC firmware at all. |

The constants are mirrored in `src/include/telemetry/ethernet/ethernet_helpers.hpp` (`AERISC_FABRIC_HEARTBEAT_SIGNATURE`) and in the fabric-view frontend at `src/frontend/static/js/fabric/constants.js`. Note that the UMD-defined `tt::umd::erisc_firmware::FABRIC_HEARTBEAT_SIGNATURE` (0xAABB) does **not** match what is actually written to L1 in practice — the value to compare against is 0xDCBA.

## Values

**Type:** Unsigned Integer

**Units:** None

**Allowable values:**
A 16-bit value (0..65535) carrying the firmware signature. See the table above for known signatures.

## Prometheus Labels

|Label Name|Value|
|---|---|
|hostname|The host from which the metric was collected.|
|hall|The datacenter hall where the host is located. Sourced from the Factory System Descriptor (FSD).|
|aisle|The datacenter aisle where the host is located. Sourced from the Factory System Descriptor (FSD).|
|rack|The rack number where the host is located. Sourced from the Factory System Descriptor (FSD).|
|shelf_u|The shelf U position in the rack where the host is located. Sourced from the Factory System Descriptor (FSD).|
|tray|The tray (UBB) that the device is located on.|
|chip|The ASIC location within the tray.|
|channel|The Ethernet channel number on the chip.|
|port_type|The physical port type (e.g., QSFP, backplane). Present when topology information is available.|
|port_id|The physical port ID. Present when topology information is available.|
|remote_hostname|The hostname of the remote endpoint. Present when remote endpoint information is available.|
|remote_tray|The tray number of the remote endpoint. Present when remote endpoint information is available.|
|remote_chip|The ASIC location of the remote endpoint. Present when remote endpoint information is available.|
|remote_channel|The Ethernet channel of the remote endpoint. Present when remote endpoint information is available.|
|remote_hall|The datacenter hall of the remote endpoint. Present when remote endpoint information is available.|
|remote_aisle|The datacenter aisle of the remote endpoint. Present when remote endpoint information is available.|
|remote_rack|The rack number of the remote endpoint. Present when remote endpoint information is available.|
|remote_shelf_u|The shelf U position of the remote endpoint. Present when remote endpoint information is available.|