atmega 128 and communication protocol

1. ATMEGA-128 &
COMMUNICATION PROTOCOL
PRESENTED BY:
Rashmi Deoli
Divya Rawat
Shalini Ranjan

2. 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

3. 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

4. BLOCK DIAGRAM

5. COMMUNICATION PROTOCOL
 In Atmega-128, there are various types of
Protocols:-
- I2C (Inter Independent Circuit).
- SPI ( Serial Peripheral Interface).
- UART (Universal Asynchronous
Receiver/Transmitter)

6. I2C Characteristics
Only 2 Wires Needed On Bus
-Serial Data (SDA)
-Serial Clock(scl)

7. How Does It Work?

8. I2C Protocol (cont.)
6. Receiver issues an ACK bit for the byte received
7. Repeat 5 and 6 if more bytes need to be transmitted
8. 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

9. 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.

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