The Microchip Technology Inc. 24LC22A is a 256 x 8-
bit dual-mode 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 (1 Kbit) and Bidirectional
mode (2 Kbit). Upon power-up, the device will be in the
Transmit-Only mode, sending a serial bit stream of the
memory array from 00h to 7Fh, clocked by the VCLK
pin. A valid high-to-low transition on the SCL pin will
cause the device to enter the Transition mode, and look
for a valid control byte on the I2C bus. If it detects a
valid control byte from the master, it will switch into
Bidirectional mode, with byte selectable read/write
capability of the entire 2K memory array using SCL. If
no control byte is received, the device will revert to the
Transmit-Only mode after it receives 128 consecutive
VCLK pulses while the SCL pin is idle. The 24LC22A is
available in standard 8-pin PDIP and SOIC packages.