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Functional Description
20BL51E00 E2

2020-03-27 Page 48
3.3.3.1 CPU Board Status LED
Table 9. CPU status LED at front panel
Error Codes
In case of an error, the LED displays the following error messages by repeatedly flashing
n times, then pausing for one second, and then repeating the error code:
Table 10. Error codes signaled via status LED flashes
3.4 Real-Time Clock (RTC)
The BL51E includes a real-time clock connected to the processor as the system RTC
(ERTC) RX-8571. The RTC has an accuracy of approximately 1.7 seconds/day (11 minutes/
year) at 25°C. The real-time clock device is connected to the CPU via SMBus.
For data retention during power off the RTC is backed up by a supercapacitor. The
supercapacitor gives an autonomy of up to 72 hours when fully charged.
Label Color Function
Yellow Indicates BL51E status messages:

On: BL51E firmware starting

Off: BL51E is switched off

Blinking: BL51E is in stand-by (S3) status

Blinking with n flashes: Error code
During normal operation the LED can be switched on and
off using software.
Number of Flashes Error
1 +3.3 V failure
2 Input voltage failure
3 External power supply failure
4 CPU too hot
5 BL51E firmware timeout
>5 Internal error
See the ACPI Specification for more details on the power states S0 to S5:
Advanced Configuration and Power Interface Specification Version 6.1
January, 2016
Unified EFI Forum
uefi.org/specifications

ERTC (External Real-Time Clock) is a real-time clock additionally
connected to the processor as a system RTC.

CRTC (Chipset Real-Time Clock) is the real-time clock of the processor.