=================== I²C bus assignments =================== The per-(sub-)bus identifiers for(/on/of) Linux-enabled UltraZohm systems are listed like **[so]**. .. _carrier_board_i2c_rev05ff: I²C on ≥Rev05 carriers ---------------------- * I²C0 (``PS_I2C0``) **[0]**: "User bus" (``I2C_USR``) with eight-channel I²C switch * ``ASlots_I2C`` **[3]**: :ref:`Per-card "UZP EEPROM"s ` * ``DSlots_I2C`` **[5]**: :ref:`Per-card "UZP EEPROM"s ` and :ref:`card-specific functions ` * ``CPLDs_I2C`` **[4]**: Primary I²C controllers of D slot CPLDs (1V8) * ``I2C_SEC`` **[7]**: Secondary I²C controller of S³C (1V8) * On Rev05 carriers, this bus is :ref:`carrier_known_issues_rev05b` * On ≥Rev06 carriers, this bus also controls the I²C GPIO of the :ref:`slot disable feature ` * ``I2C_FP_isoIOs`` **[2]**: IsoIOs on :ref:`frontpanelmainboard_rev01` and :ref:`frontpanelmainboard_rev02` * ``BP_T``/``BP_B`` **[8/6]**: Backpanels * Spare **[9]**: On ≥Rev06 carriers, this bus can be accessed via ``X3`` (NB: pull-up Rs needed!) * The bus switch/multiplexer (``U6``) can be reset via a MIO GPIO, which is helpful in case of bus lock-ups, e.g., due to downstream issues on cards etc. * I²C1 (``PS_I2C1``) **[1]**: "System bus" (``I2C_SYS``) * ``SOM_I2C``: SoM PLL and EEPROM * ``I2C_PRI``: Primary I²C controller of S³C (3V3) * ``I2C_SYS_3V3``: :ref:`Carrier "UZP EEPROM" `, frontpanel (system bus; used, e.g., for the MAC EEPROM required/included on Ethernet-enabled frontpanels), and thermal management .. _carrier_board_i2c_rev01-4: I²C on ≤Rev04 carriers ---------------------- [for reference only, please see :ref:`carrier_board_rev04_mios` et al. and their schematics for details] * I²C0 (``PS_I2C0_*``) **[0]**: SoM & adapter cards * SoM I²C (PLL and, perhaps, EEPROM) * A adapter card slots (3V3) * D adapter card slots (3V3) * D adapter card CPLDs (1V8, unused as of 2025) * I²C1 (``PS_I2C1_*``) **[1]**: Outside (connector) * Available on ``X10`` (3V3) * Used by the :ref:`carrier_retrofits_i2cssds2c` board