The PCF8584 is an integrated circuit designed in CMOS technology which serves as an interface between most standard parallel-bus microcontrollers/microprocessors and the serial I2C-bus. The PCF8584 provides both master and slave functions. Communication with the I2C-bus is carried out on a byte-wise basis using interrupt or polled handshake. It controls all the I2C-bus specific sequences, protocol, arbitration and timing. The PCF8584 allows parallel-bus systems to communicate bidirectionally with the I2C-bus.

The PCF8593 is a CMOS1 clock and calendar circuit, optimized for low power consumption. Addresses and data are transferred serially via the two-line bidirectional 2C-bus. The built-in word address register is incremented automatically after each written or read data byte. The built-in 32.768 kHz oscillator circuit and the first 8 bytes of the RAM are used for the clock, calendar, and counter functions. The next 8 bytes can be programmed as alarm registers or used as free RAM space.