CAT24C01B
SDA: Serial Data/Address
FUNCTIONAL DESCRIPTION
The CAT24C01B bidirectional serial data/address pin is
usedtotransferdataintoandoutofthedevice. TheSDA
pin is an open drain output and can be wired with other
open drain or open collector outputs.
The CAT24C01B uses a 2-wire data transmission pro-
tocol. Theprotocoldefinesanydevicethatsendsdatato
thebustobeatransmitterandanydevicereceivingdata
tobeareceiver. DatatransferiscontrolledbytheMaster
device which generates the serial clock and all START
and STOP conditions for bus access. The CAT24C01B
operates as a Slave device. Both the Master and Slave
devicescanoperateaseithertransmitterorreceiver,but
the Master device controls which mode is activated.
2-WIRE BUS PROTOCOL
The following defines the features of the 2-wire bus
protocol:
(1) Data transfer may be initiated only when the bus is
not busy.
PIN DESCRIPTIONS
(2) During a data transfer, the data line must remain
stable whenever the clock line is high. Any changes
in the data line while the clock line is high will be
interpreted as a START or STOP condition.
SCL: Serial Clock
The CAT24C01B serial clock input pin is used to clock
alldatatransfersintooroutofthedevice. Thisisaninput
pin.
Figure 1. Bus Timing
t
t
t
F
HIGH
R
t
t
LOW
LOW
SCL
t
t
SU:STA
HD:DAT
t
t
t
t
HD:STA
SU:DAT
SU:STO
BUF
SDA IN
t
t
AA
DH
SDA OUT
5020 FHD F03
Figure 2. Write Cycle Timing
SCL
SDA
8TH BIT
BYTE n
ACK
t
WR
STOP
CONDITION
START
CONDITION
ADDRESS
5020 FHD F04
Figure 3. Start/Stop Timing
SDA
SCL
5020 FHD F05
START BIT
STOP BIT
Doc. No. 25085-00 7/99 S-1
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