DS2482-100 Dallas Semiconducotr, DS2482-100 Datasheet - Page 14

• Manufacturer Part Number: DS2482-100
• Description: Single-Channel 1-Wire Master
• Manufacturer: Dallas Semiconducotr

I²C INTERFACE
General Characteristics
The I²C bus uses a data line (SDA) plus a clock signal (SCL) for communication. Both SDA and SCL are
bidirectional lines, connected to a positive supply voltage through a pullup resistor. When there is no
communication, both lines are HIGH. The output stages of devices connected to the bus must have an open-drain
or open-collector to perform the wired-AND function. Data on the I²C-bus can be transferred at rates of up to
100kbps in the standard mode, up to 400kbps in the fast mode. The DS2482 works in both modes.
A device that sends data on the bus is defined as a transmitter, and a device receiving data as a receiver. The
device that controls the communication is called a “master.” The devices that are controlled by the master are
“slaves.” To be individually accessed, each device must have a slave address that does not conflict with other
devices on the bus.
Data transfers may be initiated only when the bus is not busy. The master generates the serial clock (SCL),
controls the bus access, generates the START and STOP conditions, and determines the number of data bytes
transferred between START and STOP (Figure 8). Data is transferred in bytes with the most significant bit being
transmitted first. After each byte follows an acknowledge bit to allow synchronization between master and slave.
Figure 8. I²C Protocol Overview
Slave Address
The slave address to which the DS2482 responds is shown in Figure 9. The logic states at the address pins AD0
and AD1 determine the value of the address bits A0 and A1. The address pins allow the device to respond to one
of four possible slave addresses. The slave address is part of the slave-address/control byte. The last bit of the
slave-address/control byte (R/ W ) defines the data direction. When set to a 0, subsequent data flows from master to
slave (write access); when set to a 1, data flows from slave to master (read access).
Figure 9. DS2482 Slave Address
SDA
SCL
Idle
Condition
START
MS-bit
Most Significant Bit
1
Slave Address
2
A6
0
6
A5
0
7-Bit Slave Address
7
A4
1
R/ W
Acknowledgment
8
from Receiver
14 of 21
A3
1
ACK
ACK
bit
9
AD1, AD0 Pin
A2
0
States
AD1 AD0 R/W
A1
1
Repeated if more bytes
2
A0
are transferred
Read or Write
Determines
8
ACK
ACK
bit
9
STOP Condition
Repeated START
Condition