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CAT24WC256J-1.8TE13 View Datasheet(PDF) - Catalyst Semiconductor => Onsemi

Part Name
Description
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CAT24WC256J-1.8TE13
Catalyst
Catalyst Semiconductor => Onsemi Catalyst
CAT24WC256J-1.8TE13 Datasheet PDF : 10 Pages
1 2 3 4 5 6 7 8 9 10
CAT24WC256
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 CAT24WC256 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 bus Master begins a transmission by sending a
START condition. The Master sends the address of the
particular slave device it is requesting. The five most
significant bits of the 8-bit slave address are fixed as
10100(Fig. 5). The CAT24WC256 uses the next two bits
as address bits. The address bits A1 and A0 allow as
many as four devices on the same bus. These bits must
compare to their hardwired input pins. The last bit of the
slave address specifies whether a Read or Write opera-
tion is to be performed. When this bit is set to 1, a Read
operation is selected, and when set to 0, a Write opera-
tion is selected.
After the Master sends a START condition and the slave
address byte, the CAT24WC256 monitors the bus and
responds with an acknowledge (on the SDA line) when
its address matches the transmitted slave address. The
CAT24WC256 then performs a Read or Write operation
depending on the state of the R/W bit.
Acknowledge
After a successful data transfer, each receiving device is
required to generate an acknowledge. The Acknowledg-
ing device pulls down the SDA line during the ninth clock
cycle, signaling that it received the 8 bits of data.
The CAT24WC256 responds with an acknowledge after
receiving a START condition and its slave address. If the
device has been selected along with a write operation,
it responds with an acknowledge after receiving each 8-
bit byte.
When the CAT24WC256 begins a READ mode it trans-
mits 8 bits of data, releases the SDA line, and monitors
the line for an acknowledge. Once it receives this ac-
knowledge, the CAT24WC256 will continue to transmit
data. If no acknowledge is sent by the Master, the device
Figure 4. Acknowledge Timing
SCL FROM
1
MASTER
8
9
DATA OUTPUT
FROM TRANSMITTER
DATA OUTPUT
FROM RECEIVER
START
ACKNOWLEDGE
Figure 5. Slave Address Bits
1 0 1 0 0 A1 A0 R/W
5
Doc. No. 1031, Rev. F
 

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