The Microchip Technology Inc. 24LC21 is a 128 x 8 bit Electrically Erasable PROM. This device is designed for use in applications requiring storage and serial transmission of configuration and control information. Two modes of operation have been implemented: Transmit-only mode and Bidirectional mode. Upon power-up, the device will be in the Transmit-only mode, sending a serial bit stream of the entire memory array contents, clocked by the VCLK pin. A valid high-to-low transition on the SCL pin will cause the device to enter the Bidirectional mode, with byte selectable read/write capability of the memory array. The 24LC21 is available in a standard 8-pin PDIP and SOIC package, in both commercial and industrial temperature ranges.