Driver i2c-mlxcpld

Author: Michael Shych <>

This is the Mellanox I2C controller logic, implemented in Lattice CPLD device.

Device supports:
  • Master mode.
  • One physical bus.
  • Polling mode.

This controller is equipped within the next Mellanox systems: “msx6710”, “msx6720”, “msb7700”, “msn2700”, “msx1410”, “msn2410”, “msb7800”, “msn2740”, “msn2100”.

The next transaction types are supported:
  • Receive Byte/Block.
  • Send Byte/Block.
  • Read Byte/Block.
  • Write Byte/Block.


  • capability reg.
    Bits [6:5] - transaction length. b01 - 72B is supported, 36B in other case. Bit 7 - SMBus block read support.
CTRL 0x1
  • control reg.
    Resets all the registers.
  • cycle reg.
    Configure the width of I2C SCL half clock cycle (in 4 LPC_CLK units).
I2C_HOLD 0x5
  • hold reg.
    OE (output enable) is delayed by value set to this register (in LPC_CLK units)
CMD   0x6 - command reg. Bit 0, 0 = write, 1 = read. Bits [7:1] - the 7bit Address of the I2C device. It should be written last as it triggers an I2C transaction.
  • data size reg.
    Number of data bytes to write in read transaction
  • address reg.
    Number of address bytes to write in read transaction.
  • status reg.
    Bit 0 - transaction is completed. Bit 4 - ACK/NACK.
DATAx 0xa
  • 0x54 - 68 bytes data buffer regs.
    For write transaction address is specified in four first bytes (DATA1 - DATA4), data starting from DATA4. For read transactions address is sent in a separate transaction and specified in the four first bytes (DATA0 - DATA3). Data is read starting from DATA0.