HT1382_1105 HOLTEK [Holtek Semiconductor Inc], HT1382_1105 Datasheet - Page 16

• Manufacturer Part Number: HT1382_1105
• Description: I2C/3-Wire Real Time Clock
• Manufacturer: HOLTEK [Holtek Semiconductor Inc]

Rev. 1.40
I
2
C Serial Interface
Data Validity
START and STOP Conditions
Byte Format
The HT1382 includes an I
communication between multiple I
(SDA) and the serial clock line (SCL).Both lines are connected to the positive supply via a pull-up
resistor externally.
When the bus is free, both lines will be high. The output stages of the devices connected to the bus
must have open-drain or open-collector output types to implement the wired-AND function necessary
for connection. Data transfer is initiated only when the bus is not busy.
The data on the SDA line must be stable during the HIGH period of the clock. The HIGH or LOW state
of the data line can only change when the clock signal on the SCL line is LOW.
A HIGH to LOW transition on the SDA line while SCL is HIGH defines a START condition. A LOW
to HIGH transition on the SDA line while SCL is HIGH defines a STOP condition. START and STOP
conditions are always generated by the master. The bus is considered to be busy after the START
condition. The bus is considered to be free again a certain time after the STOP condition. The bus stays
busy if a repeated START(Sr) is generated instead of a STOP condition. In this respect, a START(S)
and repeated START(Sr) conditions are functionally identical.
Every byte put on the SDA line must be 8-bits long. The number of bytes that can be transmitted per
transfer is unrestricted. Each byte has to be followed by an acknowledge bit. Data is transferred with
the most significant bit (MSB) first.
SDA
SCL
SDA
SCL
or
Sr
S
SDA
SCL
START condition
1
S
2
Data line stable;
data valid
2
C serial interface. The I
7
2
C devices. The two lines of the interface are the serial data line
8
Change of data
ACK
16
9
allowed
I
2
1
C/3-Wire Real Time Clock
STOP condition
2
2
C bus is used for bidirectional, two-line
P
3-8
ACK
9
SDA
SCL
Sr
or
Sr
P
P
HT1382
May 27, 2011