ATMEGA48V_11 ATMEL [ATMEL Corporation], ATMEGA48V_11 Datasheet - Page 209

• Manufacturer Part Number: ATMEGA48V_11
• Description: 8-bit Atmel Microcontroller with 4/8/16K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

22. 2-wire serial interface
22.1
22.2
22.2.1
2545T–AVR–05/11
Features
2-wire serial interface bus definition
TWI terminology
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The 2-wire Serial Interface (TWI) is ideally suited for typical microcontroller applications. The
TWI protocol allows the systems designer to interconnect up to 128 different devices using only
two bi-directional bus lines, one for clock (SCL) and one for data (SDA). The only external hard-
ware needed to implement the bus is a single pull-up resistor for each of the TWI bus lines. All
devices connected to the bus have individual addresses, and mechanisms for resolving bus
contention are inherent in the TWI protocol.
Figure 22-1. TWI bus interconnection.
The following definitions are frequently encountered in this section.
Table 22-1.
Term
Master
Simple yet powerful and flexible communication interface, only two bus lines needed
Both master and slave operation supported
Device can operate as transmitter or receiver
7-bit address space allows up to 128 different slave addresses
Multi-master arbitration support
Up to 400kHz data transfer speed
Slew-rate limited output drivers
Noise suppression circuitry rejects spikes on bus lines
Fully programmable slave address with general call support
Address recognition causes wake-up when AVR is in sleep mode
Compatible with Philips I
SDA
SCL
TWI terminology.
Description
The device that initiates and terminates a transmission. The master also generates the
SCL clock.
Device 1
2
C protocol
Device 2
Device 3
........
Device n
V
ATmega48/88/168
CC
R1
R2
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