2.4 Digital Specification
31
0
5 0
Hea
der
Payload
Fig. 2.7 Format of serial data. Length of payload is variable and encoded in the header information
0
5 6 7
9 1 0
1 9 2 0
2 3 2 4
2 8 2 9
4 8 4 9
Hamming P
H PKT
Payload size
D num CH num
BXID
P
P
Fig. 2.8 Format of serial data header
Table 2.5 Protocol bit field descriptions for the serial data header
Name
Bits
Description
Hamming
6
Hamming parity bits
PH
1
Parity (even) of header
including hamming
PKT
3
Packet type, see Table 2.6
Payload size
10
Number of 10 bit words in data
payload, 11th bit is encoded in
PKT
D num
4
Device number
CH num
5
Channel number
BXID
20
Bunch-crossing identifier
(40 MHz counter)
PP
1
Parity (even) of data payload
Table 2.6 Packet type (PKT) encoding. Numbers in brackets are bit positions of the value from
Table 2.5
Data
Heartbeat Sync
Trigger
during
acq.
Payload
discarded
Payload
size [10]
PKT [2]
PKT [1]
PKT [0]
X
0
1
0
0
X
1
1
0
1
X
X
0
1
1
0
X
X
1
1
1
1
X
0
0
0
0
X
X
0
0
0
1
X
0
0
1
0
X
X
X
0
0
1
1