One main idea is to keep the possibility to replace the Master FPGA with an LpGBT chip on the final design So we need to use:

• elink data transmission
• I2C configuration

It is responsible of all communication, synchronisation and data formatting

The underlying protocol is provided by the CERN IP

The message structure is the following:

• 83 bits
• 82-83 : reserved
• 81-80: EC (unused)
• 0-79: 5 last payload long words (16 bits)
• Extra data:
  • 0-8: register address
  • 9-11: nword
  • 12-15: unused
  • 16-31: first payload long word

The message structure is the following:

• 83 bits
• 82-83 : reserved
• 81-80: EC (unused)
  • 0 never happens
  • 1 register response
  • 2 data
  • 3 never happens
• 0-79: 5 last payload long words (16 bits)
• Extra data:
  • If register response:
    • 0-8: register address
    • 9-11: nword
    • 12-15: unused
    • 16-31: first payload long word
  • if data:
    • 2 first payload words