5.6.2 Software Data Protection

A software-controlled data protection feature has been implemented on the AT28BV64B. Software data protection (SDP) helps prevent inadvertent writes from corrupting the data in the device. SDP can prevent inadvertent writes during power-up and power-down as well as during any other potential periods of system instability.

The AT28BV64B can only be written to using the software data protection feature. A series of three write commands to specific addresses with specific data must be presented to the device before writing in the byte or page mode. The same three write commands must begin each write operation. All software write commands must obey the page mode write timing specifications.

The data in the 3-byte command sequence is not written to the device; instead, the addresses in the command sequence can be utilized just like any other location in the device. Any attempt to write to the device without the 3-byte sequence will start the internal write timers. Although no data will be written to the device, for the duration of t_WC, read operations will effectively become polling operations.