SVT TRACK packet format
The Track Fitter (TF) receives
Road-Hit packets from the Hit Buffer (HB)
and fits all combination of hists in each packet. All combinations that
pass a pre-defined chi-square cut are sent in output as SVT tracks.
Each SVT track information is sent as one packet of 7 words.
Packet structure
| 24 |
23 | 22 |
21 | 20 |
19 | 18 |
17 | 16 |
15 | 14 |
13 | 12 |
11 | 10 |
9 | 8 |
7 | 6 |
5 | 4 |
3 | 2 |
1 | 0 |
| HD | DS | 0 | 0 |
1 | 0
| z out(3) | z in(3) |
phi(13)
|
| HD | DS | 0 | 0 |
road(18:17)
| sign | c(8) |
sign | d(9) |
| HD | DS | 0 | 0 |
phi sector(4) |
road(16:0) |
| HD | DS | 0 | 0 |
spare | x1(10)) |
x0(10) |
| HD | DS | 0 | 0 |
spare | x3(10)) |
x2(10) |
| HD | DS | 0 | 0 |
chi square(11)) |
x4(10) |
| HD | DS | 0 | 1 |
Track Fitter status(12) |
track number(9) |
- phi in the first word is phi of the track
as computed by the TF
- z in first word: z out = z ID of outer hit, z in = same for inner hit.
- The second word has 9 bit of signed curvature (c) and 10 of signed
impact parameter (d), most significant bit is 1 to mean negative sign.
- The curvature sign bit is 1 for negative charged tracks.
- The 3rd word contain SVT road-id and phi sector and is a copy
of the ROAD word received from the AMS via
the HB. Only the road ID bits that are actually used by the TF (15 LS bits) are passed on.
- The 4th, 5th and 6th words contain the chi square of the fit and the
cordinates of the hits in the 5 silicon layers (AM layers 0-4).
- The SVX hit coordinates are reported in abbreviated form (8 bits) as distance
from the edge of the road. The full information (14 bits) can be reconstruct from
this coordinate and the road number in word 3. The 2 MS bits of each Xi field are the long cluster flag (bit 8) and the hit existance flag (bit 9)
- The track number in the last word (7th) is simply the 9 most
significant phi bits of the XFT track as delivered to SVT by the
XTRP
i.e. the XFT wedge number. Since XFT only reports one track per wedge at
most, this number uniquely associate the SVT track to the original XFT one.
- The MSbit of the Track Fitter Status is the OR of all errors in the previous 6 bits. Bit allocation in the 12-bit TF status word is:
| TF status word bit |
bit definition |
SVT word bit # |
| 0-3 | Fit quality code | 9-12 |
| 4 | 0 (unused) | 13 |
| 5 | hit overflow | 14 |
| 6 | layer overflow | 15 |
| 7 | combinations overflow | 16 |
| 8 | invalid data | 17 |
| 9 | overflow in the fit | 18 |
| 10 | FIFO overflow | 19 |
| 11 | Error Summary = OR of the above 6 bits after a mask | 20 |
Full explanation in the document "Hardware Design and Specification
of the SVT Track Fitter" section 2.1. That is
CDF Note 5026
The 4 bit fit quality code from the TF passed to the L2 interface boards
will be forwarded to Level 2 processors. Encoded in these 4 bits are the
silicon layers with hits on the track and the layers whose hits
are wide clusters. The mapping of this data is not yet defined as of 21 Dec 99.
5 bits would be needed to completely
specify the kind of hits used, as in
Tsuyoshi's message .
The TF data are received in the Level 2 interface boards that sends a
subset of this information
to the Level 2 processors. This was true with the Alpha L2 decision system.
After the L2 decision upgrade (2005) all 7 words are received by the L2 processor.
BACK to the
SVT data words format page