The DS90UB960-Q1 implements an I2C target capable of operation supporting the Standard, Fast, and Fast-plus modes of operation allowing I2C operation at up to 1-MHz clock frequencies. Local I2C transactions to access DS90UB960-Q1 registers can be conducted 2 ms after power supplies are stable and PDB is brought high. For accesses to local registers, the I2C Target operates without stretching the clock. The primary I2C target address is set through the IDx pin. The primary I2C target address is stored in the I2C Device ID register at address 0x0. In addition to the primary I2C target address, the DS90UB960-Q1 may be programmed to respond to up to four other I2C addresses (reg 0xF8-0xFB). The four RX Port ID addresses provide direct access to the Receive Port registers without the need to set the paging controls normally required to access the port registers.