CAT1021 datasheet(9/20 Pages) CATALYST

9 / 20 page

CAT1021, CAT1022, CAT1023

Doc No. 3009, Rev. K

EMBEDDED EEPROM OPERATION

The CAT1021/22/23 feature a 2kbit embedded serial

EEPROM that supports the I2C Bus data transmission

protocol. This Inter-Integrated Circuit Bus protocol defines

any device that sends data to the bus to be a transmitter

and any device receiving data to be a receiver. The

transfer is controlled by the Master device which

generates the serial clock and all START and STOP

conditions for bus access. Both the Master device and

Slave device can operate as either transmitter or receiver,

but the Master device controls which mode is activated.

I2C Bus Protocol

The features of the I2C bus protocol are defined as

follows:

(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.

START Condition

The START Condition precedes all commands to the

device, and is defined as a HIGH to LOW transition of

SDA when SCL is HIGH. The CAT1021/22/23 monitor

the SDA and SCL lines and will not respond until this

condition is met.

STOP Condition

A LOW to HIGH transition of SDA when SCL is HIGH

determines the STOP condition. All operations must end

with a STOP condition.

DEVICE ADDRESSING

The Master begins a transmission by sending a START

condition. The Master sends the address of the particular

slave device it is requesting. The four most significant

bits of the 8-bit slave address are programmable in metal

and the default is 1010.

The last bit of the slave address specifies whether a

Read or Write operation is to be performed. When this bit

is set to 1, a Read operation is selected, and when set

to 0, a Write operation is selected.

After the Master sends a START condition and the slave

address byte, the CAT1021/22/23 monitors the bus and

responds with an acknowledge (on the SDA line) when

its address matches the transmitted slave address. The

CAT1021/22/23 then perform a Read or Write operation

depending on the R/

W bit.

tWR

STOP

CONDITION

START

CONDITION

ADDRESS

ACK

8TH BIT

BYTE n

SCL

SDA

Figure 4. Write Cycle Timing

tHIGH

SCL

SDA IN

SDA OUT

tLOW

tBUF

tSU:STO

tSU:DAT

tHD:DAT

tHD:STA

tSU:STA

tAA

tDH

Figure 3. Bus Timing

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