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All data sheets are subject to change without notice

©2001 Maxwell Technologies

All rights reserved.

256K EEPROM (32K x 8-Bit) EEPROM

28C256T

02.18.02 Rev5

This application note describes the programming procedures for the EEPROM modules and the details of various

techniques to preserve data protection.

Automatic Page Write

Page-mode write feature allows 1 to 64 bytes of data to be written into the EEPROM in a single write cycle, and allows

the undefined data within 64 bytes to be written corresponding to the undefined address (A0 to A5). Loading the first

byte of data, the data load window opens 30 µ s for the second byte. In the same manner each additional byte of data

can be loaded within 30 µ s. In case CE and WE are kept high for 100(s after data input, EEPROM enters erase and

write mode automatically and only the input data are written into the EEPROM.

WE CE Pin Operation

During a write cycle, addresses are latched by the falling edge of WE or CE, and data is latched by the rising edge of

WE or CE.

Data Polling

Data Polling function allows the status of the EEPROM to be determined. If EEPROM is set to read mode during a

write cycle, an inversion of the last byte of data to be loaded outputs from I/O 7 to indicate that the EEPROM is per-

forming a write operation.

Data Protection

To protect the data during operation and power on/off, the EEPROM has the internal functions described below.

1. Data Protection against Noise of Control Pins (CE, OE, WE) during Operation.

During readout or standby, noise on the control pins may act as a trigger and turn the EEPROM to programming mode by mis-

take. To prevent this phenomenon, the EEPROM has a noise cancellation function that cuts noise if its width is 20ns or less in

programming mode. Be careful not to allow noise of a width of more than 20ns on the control pins.