ATMEGA640 datasheet(241/436 Pages) MICROCHIP

Part #	ATMEGA640

Description	8-bit Microcontroller with 16/32/64KB In-System Programmable Flash

PDF	436 Pages

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Manufacturer	MICROCHIP [Microchip Technology]

Direct Link	http://www.microchip.com

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ATmega640/V-1280/V-1281/V-2560/V-2561/V [DATASHEET]

DS40002211A

Figure 24-8. Arbitration Between Two Masters

Note that arbitration is not allowed between:

•

A REPEATED START condition and a data bit

•

A STOP condition and a data bit

•

A REPEATED START and a STOP condition

It is the user software’s responsibility to ensure that these illegal arbitration conditions never occur. This implies

that in multi-master systems, all data transfers must use the same composition of SLA+R/W and data packets. In

other words: All transmissions must contain the same number of data packets, otherwise the result of the arbitra-

tion is undefined.

24.5 Overview of the TWI Module

The TWI module is comprised of several sub-modules, as shown in Figure 24-9 on page 242. All registers drawn in

a thick line are accessible through the AVR data bus.

SDA from

Master A

SDA from

Master B

SDA Line

Synchronized

SCL Line

START

Master A Loses

Arbitration, SDA

SDA

ATMEGA640 Datasheet(PDF) 241 Page - Microchip Technology