The bidirectional voltage level translation in the TCA6424A is provided through VCCI. VCCIshould be connected to the VCCof the external SCL/SDA lines. This indicates the VCClevel of the I2C bus to the TCA6424A. The voltage level on the P-port of the TCA6424A is determined by the VCCP.

The TCA6424A consists of three 8-bit Configuration (input or output selection), Input, Output, and Polarity Inversion (active high) registers. At power on, the I/Os are configured as inputs. However, the system controller can enable the I/Os as either inputs or outputs by writing to the I/O configuration bits. The data for each input or output is kept in the corresponding input or output register. The polarity of the Input Port register can be inverted with the Polarity Inversion register. All registers can be read by the system controller.

The system controller can reset the TCA6424A in the event of a timeout or other improper operation by asserting a low in theRESETinput. The power-on reset puts the registers in their default state and initializes the I2C/SMBus state machine. TheRESETpin causes the same reset/initialization to occur without depowering the part.Read more