1.5.2 PPC-formatted data

  Data having been formatted by the PPC always start with a control word.

PPC Data Header Word

        BBxxxxxx'xxxxxxxx'xxllllll'llllllll

B:      2-bit subbranch: 00-CST; 01-BST; 10-VLQ
x:      subbranch specific (containing the PPC no. somewhere)
l:      14-bit length of PPC data block (in long words)
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Offline, formatted data from one specific PPC within the SIFE bank can then be identified by their branch, PPC number, and the length. The header word is followed by a nine-word header block. These words can contain any information, e.g.

• values from the PPC's timing register
• ``Code version'' labels
• debug information

After the header follows the PPC data block. Look into the detector specific sections for its description. The header provides a safe way to check for formatted data: word 6 is used by both CST and BST as a code version label: the word found there is 0xC0DExxxx. Hence asking for the MSW of header word 6 to be 0xC0DE means selecting formatted data.