X4643 XICOR [Xicor Inc.], X4643 Datasheet - Page 9

• Manufacturer Part Number: X4643
• Description: CPU Supervisor with 64K EEPROM
• Manufacturer: XICOR [Xicor Inc.]

X4643/5 – Preliminary Information
Serial Write Operations
B
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
Figure 8. Byte Write Sequence
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
Figure 9. Page Write Operation
REV 1.26 4/30/02
YTE
W
Signals from
Signals from
RITE
SDA Bus
the Master
the Slave
Signals from
Signals from
the Master
the Slave
SDA Bus
S
a
r
t
1
0
1
Slave
0
S
a
r
t
1
0
0
1
C
A
Slave
0
Word Ad-
0
A
C
K
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Word Address
Byte 1
C
A
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.
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.
Word Ad-
C
A
K
Word Address
Byte 0
A
C
Characteristics subject to change without notice.
Data
A
C
K
(1 < n < 64)
Data
A
C
Data
A
C
K
S
o
t
A
C
S
o
t
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