== TTC Bus ==

=== TTC connector pinout ===

||pin pair||signal||description||
||1, 2||spill||Trigger and data readout enable||
||3, 4||parity||Odd parity of spill and trigger signals||
||5, 6||trigger||Trigger signal||
||7, 8||clock||41.667 MHz clock signal||
||9, 10||ground||TTC bus signal ground||
Even signal pin positive.

Spill, trigger and parity signals have width 50 ns and are synchronous to clock.


Connector: 2.54 mm 2x5 (10 pins).

Connector part numbers: AMP - 1658621-1

=== Signal Timing ===

||<:-2>measurement||<:>min||<:>typ||<:>max||
||<:-2>''clock'' frequency|| || 41.666667 MHz ±0.001% || ||
||<:|2>''spill'', ''parity'', ''trigger''|| setup time, ns || ||8.5||10.0||
||hold time, ns ||5.0||6.0|| ||

Timing provided by design TTCM v2.0 firmware rev.8512
{{{
1 ns step

CLK  ___/^^^^^^^^^\_________/^^^^^^^^^\_________/^^^

TRIG ________XXXXXXX^^^^^^^^^^^^^XXXXXXX__________...

                    | setup |hold|
}}}

=== TTC 2.0 Timecode Extension ===

Spill signal is used as a gate for data acquisition. Trigger signal is used only when spill signal is active.

In order to provide TAI timecode to modules an extension of TTC standard is proposed, TTC 2.0.

With spill signal low, trigger line become an encoded serial data channel, 40 Mbps data rate. Timecode information is transmitted serially using 8b10b encoding and K28.5 comma symbol as idle code. Big endian byte order. A sequence of data coded forms a frame.

TAI timecode is encoded as [[TAI 64-bit Timestamp]].

==== Frame Type 1: Timecode ====

Frame type 1 transmission time: 25 ns * 20 words * 10 bit = 5 µs. The moment of beginning of first bit of frame corresponds to TAI timecode data being transferred.

||Byte||||
||0||Frame type||
||1||TAI seconds [39:32]||
||2||TAI seconds [31:24]||
||3||TAI seconds [23:16]||
||4||TAI seconds [15:8]||
||5||TAI seconds [7:0]||
||6||TAI nanoseconds [29:22]||
||7||TAI nanoseconds [21:14]||
||8||TAI nanoseconds [13:6]||
||9||TAI nanoseconds [5:0], flags[1:0]||
||10||spill_id[31:24]||
||11||spill_id[23:16]||
||12||spill_id[15:8]||
||13||spill_id[7:0]||
||14||reserved||
||15||reserved||
||16||CRC32[31:24]||
||17||CRC32[23:16]||
||18||CRC32[15:8]||
||19||CRC32[7:0]||

 * TAI - International Atomic Time
 * flags[3:0] = {time_valid, ptp_wr_mode, ptp_mode, ntp_mode}
 * CRC32 use Ethernet 802.3 polinom

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[[CategoryTTC|TTC]] [[CategoryWhiteRabbit|WhiteRabbit]]