This page describes the proposed Rev 2 version of the CMS TTT.
This module essentially provides encoding and decoding of the fibre optic
protocol used by the LHC TTC system.

The proposed Rev 2 version will have the following enhancements over
the original:

* Careful clock distribution to FPGA
* More (4?) fibre links
* Gigabit Ethernet (SFP); IPBus v2
* Substantially larger FPGA to support above requirements
* Eliminate or move to non-front-panel connector the TTS (RJ-45 I/O)

I/O should be as follows:

* 4X SFP for TTC signalling
* 1X SFP for Gigabit Ethernet
* Clock in
* Clock out
* 3-4 NIM logic inputs (BC0, L1A, spares)
* 3-4 NIM logic outputs (BC0, L1A, spares)

=== Reference ===
* [[TTTT Users Manual]]
* [[TTTT Debugging]]
* [[TTTT TODO]]


* [[CMS_TTT-TTS_TTC_Tester]] -- V1 board documentation
* TTCci schematic:  [http://ohm.bu.edu/~hazen/CMS/EDA-00650-V6_sch.pdf EDA-00650-V6_sch.pdf]
* TTCex schematic:  [http://ohm.bu.edu/~hazen/CMS/ttcex.1.pdf P1]  [http://ohm.bu.edu/~hazen/CMS/ttcex.2.pdf P2]  [http://ohm.bu.edu/~hazen/CMS/ttcex.3.pdf P3] 

Some explanation of the CERN modules:  The [http://cmsdoc.cern.ch/cms/TRIDAS/ttc/modules/ttcci/ TTCci] is
a module developed for CMS which provides much of the same functionality we need, but is output-only.
It has both A/B electrical outputs which would drive a TTCex module, but also a high-power laser which
can drive 32 loads through a passive optical splitter.

The TTCex receives the A/B optical signals plus clock and has 10 high-power laser outputs.

The high-power laser output may be a problem.  The TTCci used a PT5343 which is obsolete.
See [http://indico.cern.ch/getFile.py/access?resId=1&materialId=slides&confId=12273 Slide 8] for
some more info.  The chosen OCP STX03 seems also to be obsolete.