CAT28C257

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7

Page Write

The page write mode of the CAT28C257 (essentially an

extended BYTE WRITE mode) allows from 1 to 128 bytes

of data to be programmed within a single EEPROM write

cycle. This effectively reduces the byte−write time by a

factor of 128.

Following an initial WRITE operation (WE pulsed low,

issuing sequential WE pulses, which load the address and

data bytes into a 128 byte temporary buffer. The page

can be loaded in any order) during the first and subsequent

write cycles. Each successive byte load cycle must begin

pulse. There is no page write window limitation as long as

Upon completion of the page write sequence, WE must

program cycle to commence. This programming cycle

consists of an erase cycle, which erases any data that existed

in each addressed cell, and a write cycle, which writes new

data back into the cell. A page write will only write data to

the locations that were addressed and will not rewrite the

entire page.

Figure 6. Byte Write Cycle [CE Controlled]

ADDRESS

DATA OUT

DATA IN

DATA VALID

HIGH−Z

WE

OE

CE

Figure 7. Page Mode Write Cycle

ADDRESS

I/O

BYTE 0

BYTE 1

BYTE 2

BYTE n

BYTE n+1

BYTE n+2

LAST BYTE

WE

CE

OE