I2C总线扩展器：This application note describes two PLD designs made with the PLC42VA12. Both designs are controller functions for an I2C-bus n-bit I/O expander. The first design isa controller function for a n-bit I2C-bus Input Expansion (I2C-bus Slave Transmitterfunction) and the second one for a n-bit I2C-bus Output Expansion (I2C-bus SlaveReceiver function).The I2C-bus is a 2-way, 2-line communicationbetween different ICs or modules. The two lines are a serial data line (SDA) and a serialclock line (SCL). The designs provide remoteinput or output expansion for our Philipsmicro controller families via the two-line serialbidirectional I2C-Bus. The I2C-Bus slaveaddress of the designs is equal to theaddress of the PCF8574 (remote 8-bit I/O expander). The I2C-Bus has been specified for 100kHz, but the PLC42VA12 designs can go up to 1MHz. This makes the designs suitable as test vehicle for the new fast I2C-Bus standard of 400 kHz.