X4643 datasheet(9/22 Pages) XICOR

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X4643/5 – Preliminary Information

Characteristics subject to change without notice.

9 of 22

REV 1.26 4/30/02

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Serial Write Operations

BYTE WRITE

For a write operation, the device requires the Slave

Address Byte and a Word Address Byte. This gives the

master access to any one of the words in the array. After

receipt of the Word Address Byte, the device responds

with an acknowledge, and awaits the next eight bits of

data. After receiving the 8 bits of the Data Byte, the

device again responds with an acknowledge. The mas-

ter then terminates the transfer by generating a stop

condition, at which time the device begins the internal

write cycle to the nonvolatile memory. During this inter-

nal write cycle, the device inputs are disabled, so the

device will not respond to any requests from the master.

The SDA output is at high impedance. See Figure 8.

Figure 8. Byte Write Sequence

Slave

Word Address

Byte 0

Data

SDA Bus

Signals from

the Slave

Signals from

the Master

Word Address

Byte 1

A write to a protected block of memory will suppress

the acknowledge bit.

Page Write

The device is capable of a page write operation. It is

initiated in the same manner as the byte write opera-

tion; but instead of terminating the write cycle after the

ﬁrst data byte is transferred, the master can transmit

an unlimited number of 8-bit bytes. After the receipt of

each byte, the device will respond with an acknowl-

edge, and the address is internally incremented by

one. The page address remains constant. When the

counter reaches the end of the page, it “rolls over” and

goes back to ‘0’ on the same page. This means that the

master can write 64-bytes to the page starting at any

location on that page. If the master begins writing at

location 60, and loads 12-bytes, then the ﬁrst 4-bytes

are written to locations 60 through 63, and the last

8-bytes are written to locations 0 through 7. After-

wards, the address counter would point to location 8 of

the page that was just written. If the master supplies

more than 64-bytes of data, then new data over-writes

the previous data, one byte at a time.

Figure 9. Page Write Operation

Slave

Word Ad-

Data

SDA Bus

Signals from

the Slave

Signals from

the Master

Data

(1 < n < 64)

Word Ad-

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