Symmetricom XLi IEEE 1588 manual Nasa 36 Code Format

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Coordinated Time (UTC) in 24 hour format and not local time. Nonetheless, this instrument can encode UTC or local time in either 24 or 12 hour formats.

NASA 36 Code Format

The level shifted, pulse width modulated, serial format of NASA 36 is divided into two segments. The first segment encodes time of year in binary coded decimal (BCD) notation. The second segment encodes control functions (unused on Model XLi).

The two code segments are contained within one "frame". The frame length for NASA 36 is 1 second long and contains 100 "elements" (pulses) each of which start every 10 milliseconds.

An element may represent either a binary zero, a binary one, a reference marker or a position identifier. A zero is 2 ms, a one is 6 ms, a position identifier is 6 ms. A reference marker is 5 consecutive position identifiers. A reference marker locates the beginning of each frame.

Output

The XLi provides the following NASA 36 time code outputs:

NASA 36 (AM):1 KHz sine wave amplitude modulated BCD

NASA 36 (DC):DC level shift, width coded BCD

Input

The XLi can also synchronize and lock to the following NASA 36 input codes.

NASA 36 (AM):1 KHz sine wave amplitude modulated BCD

NASA 36 (DC):DC level shift, width coded BCD

XLi IEEE 1588 Clock 191

997-01510-03, Rev. C, 12/12/2006