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35
8068C–AVR–06/08
XMEGA A3
19. TWI - Two Wire Interface
19.1
Features
•
Two Identical TWI peripherals
•
Simple yet Powerful and Flexible Communication Interface
•
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 400 kHz 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 in Sleep Mode
•
I
2
C and System Management Bus (SMBus) compatible
19.2
Overview
The Two-
W
ire Interface (T
W
I) is a bi-directional wired-AND bus with only two lines, the clock
(SCL) line and the data (SDA) line. The protocol makes it possible to interconnect up to 128 indi-
vidually addressable devices. Since it is a multi-master bus, one or more devices capable of
taking control of the bus can be connected.
The only external hardware needed to implement the bus is a single pull-up resistor for each of
the T
W
I bus lines. Mechanisms for resolving bus contention are inherent in the T
W
I protocol.
PORTC and PORTE each has one T
W
I. Notation of these peripherals are T
W
IC and T
W
IE.