CAT1161 Catalyst Semiconductor, CAT1161 Datasheet - Page 7

• Manufacturer Part Number: CAT1161
• Description: Supervisory Circuits with I2C Serial CMOS EEPROM/ Precision Reset Controller and Watchdog Timer
• Manufacturer: Catalyst Semiconductor

FUNCTIONAL DESCRIPTION
The CAT1161/2 supports the I
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
SDA when SCL is HIGH. The CAT1161/2 monitors the
SDA and SCL lines and will not respond until this
condition is met.
Figure 6. Slave Address Bits
**a8, a9 and a10 correspond to the address of the memory array address word.
Figure 5. Acknowledge Timing
2
C Bus Protocol
CAT1161/2
CAT
FROM TRANSMITTER
24C163
FROM RECEIVER
DATA OUTPUT
DATA OUTPUT
2
C bus protocol are defined as
SCL FROM
MASTER
1
2
C Bus data transmission
0
START
1
0
1
a10
7
a9
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 fixed as 1010.
The next three bits (Figure 6) define memory addressing.
For the CAT1161/162 the three bits define higher order
bits.
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 CAT1161/2 monitors the bus and
responds with an acknowledge (on the SDA line) when
its address matches the transmitted slave address. The
CAT1161/2 then performs a Read or Write operation
depending on the R/W bit.
a8
R/W
8
ACKNOWLEDGE
9
Doc No. 3002, Rev. D
CAT1161/2