CAT1027 CATALYST [Catalyst Semiconductor], CAT1027 Datasheet - Page 9

• Manufacturer Part Number: CAT1027
• Description: Dual Voltage Supervisory Circuits with I2C Serial 2k-bit CMOS EEPROM
• Manufacturer: CATALYST [Catalyst Semiconductor]

EMBEDDED EEPROM OPERATION
The CAT1026 and CAT1027 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
Figure 4. Bus Timing
Figure 5. Write Cycle Timing
2
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
device, and is defined as a HIGH to LOW transition of
SDA when SCL is HIGH. The CAT1026 and CAT1027
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 CAT1026 and CAT1027 monitor the
bus and responds with an acknowledge (on the SDA
line) when its address matches the transmitted slave
address. The CAT1026 and CAT1027 then perform 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
CAT1026, CAT1027
ADDRESS
Doc No. 3010, Rev. K