The AT93C66B-SSHM-B is a MICROWIRE-compatible 4kB 3-wire serial Electrically Erasable Programmable Read-Only Memory (EEPROM) organized as 512 words of 16-bit each (when the ORG pin is connected to VCC) and 256 words of 8-bit each (when the ORG pin is tied to ground). The device is optimized for use in many industrial and commercial applications where low-power and low-voltage operations are essential. The AT93C66B is enabled through the chip select pin (CS) and accessed via a 3-wire serial interface consisting of data input (DI), data output (DO) and shift clock (SK). Upon receiving a read instruction at DI, the address is decoded and the data is clocked out serially on the DO pin. The write cycle is completely self-timed and no separate erase cycle is required before write. The write cycle is only enabled when the part is in the erase/write enable state. When CS is brought high following the initiation of a write cycle, the DO pin outputs the ready/busy status of the part.