CAT24C01B

4

Doc. No. 25085-00 7/99 S-1

FUNCTIONAL DESCRIPTION

The CAT24C01B uses a 2-wire data transmission pro-

tocol. The protocol defines any device that sends data to

the bus to be a transmitter and any device receiving data

to be a receiver. Data transfer is controlled by the Master

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

devices can operate as either transmitter or receiver, but

the Master device controls which mode is activated.

PIN DESCRIPTIONS

SCL: Serial Clock

The CAT24C01B serial clock input pin is used to clock

all data transfers into or out of the device. This is an input

pin.

SDA: Serial Data/Address

The CAT24C01B bidirectional serial data/address pin is

used to transfer data into and out of the device. The SDA

pin is an open drain output and can be wired with other

open drain or open collector outputs.

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.

(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.

Figure 2. Write Cycle Timing

Figure 1. Bus Timing

Figure 3. Start/Stop Timing

5020 FHD F05

5020 FHD F04

5020 FHD F03

tHIGH

SCL

SDA IN

SDA OUT

tLOW

tF

tLOW

tR

tBUF

tSU:STO

tSU:DAT

tHD:DAT

tHD:STA

tSU:STA

tAA

tDH

tWR

STOP

CONDITION

START

CONDITION

ADDRESS

ACK

8TH BIT

BYTE n

SCL

SDA

START BIT

SDA

STOP BIT

SCL