X24128
PIN DESCRIPTIONS
Serial Clock (SCL)
The SCL input is used to clock all data into and out of
the device.
Serial Data (SDA)
SDA is a bidirectional pin used to transfer data into and
out of the device. It is an open drain output and may be
wire-ORed with any number of open drain or open col-
lector outputs.
An open drain output requires the use of a pull-up
resistor. For selecting typical values, refer to the Pull-
up resistor selection graph at the end of this data
sheet.
Device Select (S
0
, S
1
, S
2
)
The device select inputs (S
0
, S
1
, S
2
) are used to set
the first three bits of the 8-bit slave address. This
allows up to eight devices to share a common bus.
These inputs can be static or actively driven. If used
statically they must be tied to V
SS
or V
CC
as appropri-
ate. If actively driven, they must be driven with CMOS
levels (driven to V
CC
or V
SS
).
Write Protect (WP)
The Write Protect input controls the Hardware Write
Protect feature. When held LOW, Hardware Write Pro-
tection is disabled. When this input is held HIGH, and
the WPEN bit in the Write Protect Register is set HIGH,
the Write Protect Register is protected, preventing
changes to the Block Lock protection and WPEN bits.
PIN NAMES
Symbol
S
0
, S
1
, S
2
SDA
SCL
WP
V
SS
V
CC
NC
S
0
S
1
NC
NC
NC
S
2
V
SS
8-Lead XBGA: Top View
WP
1
V
CC
2
SDA
3
SCL
4
8
S1
7
S0
6
V
SS
5
S2
PIN CONFIGURATION
14 Lead SOIC
1
2
3
4
5
6
7
14
13
12
X24128
11
10
9
8
V
CC
WP
NC
NC
NC
SCL
SDA
DEVICE OPERATION
The device supports a bidirectional bus oriented proto-
col. The protocol defines any device that sends data
onto the bus as a transmitter, and the receiving device
as the receiver. The device controlling the transfer is a
master and the device being controlled is the slave.
The master will always initiate data transfers, and pro-
vide the clock for both transmit and receive operations.
Therefore, the device will be considered a slave in all
applications.
Clock and Data Conventions
Data states on the SDA line can change only during
SCL LOW. SDA state changes during SCL HIGH are
reserved for indicating start and stop conditions. Refer
to Figures 1 and 2.
Start Condition
All commands are preceded by the start condition,
which is a HIGH to LOW transition of SDA when SCL is
HIGH. The device continuously monitors the SDA and
SCL lines for the start condition and will not respond to
any command until this condition has been met.
Description
Device Select Inputs
Serial Data
Serial Clock
Write Protect
Ground
Supply Voltage
No Connect
REV 1.1 9/8/00
www.xicor.com
Characteristics subject to change without notice.
2 of 16
XICOR [ XICOR INC. ]
