171 CBU 78090, 171 CBU 98090 and 171 CBU 98091 CPU Status LEDs

CPU Status LEDs

The LED panel on the 171 CBU 78090, 171 CBU 98090 and 171 CBU 98091 processors includes the following LEDs you can use to diagnose the CPU status:

The state of each of these 3 LEDs–blinking, ON, or OFF–collectively describe the CPU status, as follows:

RUN	ERR	I/O	CPU State
Blinking¹	Blinking¹	Blinking¹	The CPU is booting, or is performing power-up self tests, or detects a missing or invalid OS.
OFF	Blinking¹	OFF	The CPU is not configured.
Blinking¹	OFF or Blinking¹	OFF or ON	A valid application is in the CPU. The CPU is in stop state. A blinking ERR LED indicates that a minor CPU error has been detected. The processor can continue to operate. Solid ON I/O LED indicates a local I/O error or an I/O-Bus error has been detected.
ON	OFF or Blinking¹	OFF or ON	The CPU is in run mode.
Blinking¹	ON	OFF	A firmware transfer is in progress.
1. ON for 250 ms, OFF for 250 ms, repeated continuously.