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Status LEDs

TSync Time Code Processor cards include three LEDs that provide visual status information. See table LED Colors below for these indicator codes.

The LEDs operate in certain modes by default, but each LED can be programmed independently to display any mode, including a manual mode. In manual mode, the LEDs are user-configurable to ON, OFF, or BLINK. For additional information, see the TSync Factory Driver Guide, Section (

LED colors

LED Color Function Meaning
green SYNC Unit is synchronized: A valid external time or 1PPS reference is present, disciplining the onboard oscillator.
yellow HOLDOVER Unit is in holdover: No valid external reference is present. The onboard oscillator is not disciplined by an external reference, but continues to provide time/frequency for the duration of the user-set holdover time (default = 7200 seconds [= 2 hours]).
red ALARM The unit does not provide a time or frequency signal.

During the states power-on, self-test, wait-for-host, and download-from-host, modes are directly allocated to the LEDs, as listed below.

During normal operation, the LEDs can indicate any operational mode, as programmed by the user.

LED flash patterns

State Color/FUNCTION
green/SYNC yellow/HOLDOVER red/ALARM
Power-On On Off Off
Self-Test On On On
Waiting for Host Blink Off Blink
Download from Host Strobe Strobe Strobe
Initialize Off Off Off
Never Synchronized Off Off Off
Synchronized On Off Off
Holdover On On Off
No Longer Synchronized Off Off On
Free Run Blink Blink Off
Fault Code Code Code

The Fault state is indicated by the blinking code. It blinks the number of times indicated below, with a 2-second pause between each set.

Fault codes

No. of Blinks Meaning
1 FPGA programming error
2 Failure to decompress
3 CRC failure writing to flash
4 Self-test failure
5 Timing system failure