CAT1025 CATALYST [Catalyst Semiconductor], CAT1025 Datasheet - Page 9

• Manufacturer Part Number: CAT1025
• Description: Supervisory Circuits with I2C Serial 2k-bit CMOS EEPROM and Manual Reset
• Manufacturer: CATALYST [Catalyst Semiconductor]

EMBEDDED EEPROM OPERATION
The CAT1024 and CAT1025 feature a 2kbit embedded
serial EEPROM that supports the I
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.
I
The features of the I
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
Figure 3. Bus Timing
2
Figure 4. Write Cycle Timing
C Bus Protocol
SCL
SDA
SDA OUT
SDA IN
SCL
t SU:STA
2
C bus protocol are defined as
8TH BIT
BYTE n
t F
t HD:STA
t LOW
ACK
2
C Bus data
t AA
t HD:DAT
t HIGH
STOP
CONDITION
9
t LOW
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.
t DH
t SU:DAT
t R
t WR
START
CONDITION
t SU:STO
t BUF
CAT1024, CAT1025
ADDRESS
Doc No. 3008, Rev. M