This document discusses several data communication standards used in embedded systems, including RS-232, RS-422, RS-485, CAN, SPI, and I2C. It describes the key features and protocols of each standard. RS-232 is an older standard serial port that was commonly used to program microcontrollers but has been replaced by newer standards like JTAG and USB. RS-422 and RS-485 are balanced differential standards suitable for long-distance transmission over twisted pair cabling. CAN is a robust protocol developed for vehicle networks to interconnect electronic control units. SPI and I2C are common synchronous serial bus standards used for communication between integrated circuits.

1. DATA COMMUNICATION
STANDARDS
III YEAR EEE
EE 8691- EMBEDDED SYSTEMS
UNIT-2
K.BALAJI , AP/ECE, SSMCE

2. EMBEDDED SYSTEMS-
RS 232 STANDARD
• Standard Serial Port – Back of PC
• Used to
– download the Program to Microcontroller
from PC
• Replaced by JTAG, USB
• Conversion Cable can be used
• Hyperterminal- PC to serial Port
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3. RS 232 STANDARD
• Sending DATA as bits – ‘1’ or ‘0’
• TTL – bit-’1’ : 5V
• TTL – bit- ‘0’ : 0V
• TTL Levels– not suitable for Long
distance transmission ????????????
• RS232- Bit - 1: -3V to -25V
• Bit – 0: +3V to +25 V
K.BALAJI , AP/ECE, SSMCE

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9. RS 422 / RS 485
• Used in Instrumentation Systems
• Balanced , Differential
• V+, V- , No Ground
• Low Noise Differential Signaling
• Twisted Pair Cabling
• 1200 Metres
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10. RS 422 / RS 485
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11. RS 422 / RS 485
• RS 422 – MultiDrop Protocol
– One Central Control Unit can send
commands in parallel to 10 slaves
• RS 485 – MultiPoint Protocol
– All Nodes are equal
– Every Node has send and receive
capabilities
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13. CONTROLLER AREA NETWORK (CAN)
• CAN is a Protocol developed to
reduce wiring inside vehicles
• It is used to interconnect Engine
Control Unit, Transmission Control
Unit, Door Locks
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14. CAN PROTOCOL
• CASE-I: ONE NODE SENDS A
MESSAGE
– One Node Broadcast a message
– The receiving nodes test the identifier
– Accept if it is relevant
K.BALAJI , AP/ECE, SSMCE

15. CAN PROTOCOL
• CASE-II: MANY NODES SENDS A
MESSAGE
– One node is allowed to do a valid
Broadcats
– Using Arbitration Mechanism
– 0- called Dominant
– 1 – called Recessive
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18. FEATURES OF CAN
• Differential Signalling
• Resistant to noise
• NRZ Coding
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19. CAN DATA FRAME
• SOF- START OF FRAME
• 11 BIT IDENTIFIER
• RTR- TO TELL ANY OTHER NODE TO TRANSMIT
• CONTROL FIELD : 6 BITS
• DATA : 0 TO 64 BYTES
• CRC : TO CHECK ERROR
• 2 BIT ACKNOWLEDGEMENT FIELD
• 7 BIT END OF FRAME
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20. SPI BUS
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24. I2C – INTER INTEGRATED CIRCUIT BUS
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28. REFERENCES:
1. Raj Kamal, ‘Embedded System-Architecture,
Programming, Design’, Mc Graw Hill, 2013.
2. Dr.G.Ram Prabhu, Embedded Systems
K.BALAJI , AP/ECE, SSMCE