CAT1024(2004) Просмотр технического описания (PDF) - Catalyst Semiconductor => Onsemi

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CAT1024
(Rev.:2004)

Supervisory Circuits with I2C Serial 2k-bit CMOS EEPROM and Manual Reset

Catalyst Semiconductor => Onsemi 

CAT1024, CAT1025

EMBEDDED EEPROM OPERATION

The CAT1024 and CAT1025 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 CAT1024/25 monitors 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 CAT1024/25 monitors the bus and

responds with an acknowledge (on the SDA line) when

its address matches the transmitted slave address. The

CAT1024/25 then performs a Read or Write operation

depending on the R/W bit.

Figure 3. Bus Timing

tF

tHIGH

tR

tLOW

tLOW

SCL

tSU:STA

tHD:DAT

tHD:STA

tSU:DAT

SDA IN

SDA OUT

tAA

tDH

tSU:STO

tBUF

Figure 4. Write Cycle Timing

SCL

SDA

8TH BIT

BYTE n

ACK

tWR

STOP

CONDITION

9

START

CONDITION

ADDRESS

Doc No. 3008, Rev. M

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