ATMEGA-128 & COMMUNICATION PROTOCOL

PRESENTED BY:Rashmi Deoli

Divya Rawat

Shalini Ranjan

ATMEGA 128 DESCRIPTION

• It is the high performance• Low power ATMEL• 8 bit AVR• RISC based microcontroller-128 kb programmable flash memory• JTAG interface on chip debugging• It operates between 4.5-5.5 volts• Pin count -64• No USB interface

Atmel Atmega128 Overview

MEMORY SYSTEM:-

There are four separate memory spaces on the AVR. Program space: -128K byte (64Kx16) in-circuit flash programmable. -Can be accessed by program for storage of constants.

SRAM Data Memory:-4K bytes

-variable storage area

EEPROM:-4K bytes-separate data space

BLOCK DIAGRAM

COMMUNICATION PROTOCOL

In Atmega-128, there are various types of Protocols:-

- I2C (Inter Independent Circuit). - SPI ( Serial Peripheral Interface).

- UART (Universal Asynchronous Receiver/Transmitter)

I2C Characteristics

Only 2 Wires Needed On Bus-Serial Data (SDA)-Serial Clock(scl)

How Does It Work?

I2C Protocol (cont.)

6. Receiver issues an ACK bit for the byte received7. Repeat 5 and 6 if more bytes need to be transmitted8. Master always sends stop condition (P)

a. For write transaction (master transmitting), master issues stop condition (P) after last byte of data.b. For read transaction (master receiving), master does not acknowledge final byte, just issues stop condition (P) to tell the slave the transmission is done

ADVANTAGES• Only two signal lines requires• Flexible data transmission rates

• Each device on the bus is independently addressable• Devices have a simple Master/Slave relationship.

References

I2C: http://www-us2.semiconductors.philips.com/acrobat/various/ http://www.esacademy.com/faq/i2c/index.htm http://www.embedded.com/story/OEG20020528S0057