AT90USB646 datasheet(211/456 Pages) ATMEL

211 / 456 page

211

7593L–AVR–09/12

AT90USB64/128

21. 2-wire serial interface

21.1

Features

• 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

21.2

2-wire Serial Interface bus definition

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 21-1. TWI bus interconnection.

21.2.1

TWI terminology

The following definitions are frequently encountered in this section.

The Power Reduction TWI bit, PRTWI bit in “PRR0 – Power Reduction Register 0” on page 54

must be written to zero to enable the 2-wire Serial Interface.

Device 1

Device 2

Device 3

Device n

SDA

SCL

........

Table 21-1.

TWI terminology.

Term

Description

Master

The device that initiates and terminates a transmission. The Master also generates the

SCL clock.

Slave

The device addressed by a Master.

Transmitter

The device placing data on the bus.

Receiver

The device reading data from the bus.

AT90USB646 Datasheet(PDF) 211 Page - ATMEL Corporation

AT90USB646 Datasheet(HTML) 211 Page - ATMEL Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL