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Communication lines

Communication lines. OSI model. Open Systems Interconnection (OSI) model (ISO/IEC 7498-1). Physical layer – specifies electrical and physical properties (cable) Pins, voltages, impedance, modulation, timing, topology. Source: homepages.uel.ac.uk . OSI model.

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Communication lines

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  1. Communication lines

  2. OSI model • Open Systems Interconnection (OSI) model (ISO/IEC 7498-1) • Physical layer – specifies electrical and physical properties (cable) • Pins, voltages, impedance, modulation, timing, topology Source: homepages.uel.ac.uk

  3. OSI model • Open Systems Interconnection (OSI) model (ISO/IEC 7498-1) • Physical layer – Transmits raw bit stream over physical cable • IEEE 802, RS232, RS422, RS485, I2C, SPI,… Source: homepages.uel.ac.uk

  4. OSI model • Open Systems Interconnection (OSI) model (ISO/IEC 7498-1) • Data link layer – specifies network data frame (packet), checksum, source and destination address, and data • E.g. Ethernet MAC, RS232 Source: homepages.uel.ac.uk

  5. OSI model • Open Systems Interconnection (OSI) model (ISO/IEC 7498-1) • Network layer – routing, directing datagrams from one network to another • E.g. IP addresses Source: homepages.uel.ac.uk

  6. RS232 (EIA232) • Dates from 1969 (RS-232-C) • Last standard is TIA/EIA-232-F from 1997 • Defines physical and data link layer • Single transmitter and receiver RX TX Log. 0 : > +3 V Log. 1 : < -3 V Log. 0 : +5 to +15 V Log. 1 : -15 to -5 V Noise immunity: min. 2 V

  7. RS232 (EIA232) RX TX • Length RS-232-C = 15 m • RS-232-F defines max. load capacity 2500 pF signal CRX CS CM CS ~20 pF shield

  8. RS232 - Cable capacity signal CRX CS CS ~ 0,5 CM unshielded cable CS ~ 2 CM shielded cable CM CS ~20 pF shield Max. length: Lmax = 2500 / Ctotal Ctotal = CM + CS e.g. Belden 1700A TP: 78,7 Ω/km, 45,9 pF/m

  9. RS232 - Communication protocol Log. 0 : +5 to +15 V Log. 1 : -15 to -5 V data: 11010101b (213dec) idle • Odd • Even start (parity) 0 0 0 0 1 1 1 1 1 1 stop b0 idle b2 b4 b6 b1 1,1.5,2 b3 b5 b7 LSB MSB

  10. RS232 - Asynchronous communication Fixed comm. speed: tx + rx same (tolerance ~3%) idle RX TX start (parity) 0 0 0 0 1 1 1 1 1 1 stop b0 idle b2 b4 b6 b1 b3 b5 b7

  11. RS232 - Communication speed RS-232-F limits to 30 V/µs, max 4% of bit time => max. theoretical speed 200 kbit/s 0 ΔV 1 1 Δt

  12. RS232 - Communication speed RS-232-F standard definesspeeds: 50,75,110,150,300,600,1200,2400,4800,9600,19200 bit/s Common speeds above standard definition: 28800, 38400, 57600, 115200 bit/s Higher speed = lower distance source: www.hw.cz

  13. RS232 - Signals RxD TxD Dev. 1 Dev. 2 RxD TxD RTS CTS Request to send RTS CTS Clear to send Data Carrier Detect DTR Data terminal ready DCD DSR Data Set Ready DCD DSR DTR GND

  14. RS232 - Connectors source: www.arcelect.com 9 pin

  15. RS232 - Connectors 25 pin source: fjkraan.home.xs4all.nl source: www.solentcables.co.uk

  16. RS232 - Summary • 1 transmitter, 1 receiver • Common ground • Typically 8 bit, no parity, 1 stop bit (8N1)

  17. RS-422 (EIA-422) • ANSI/TIA/EIA-422-B or ITU-T Recommendation T-REC-V.11 • Uses differential signaling + GND • 1 transmitter + 10 receivers • 10 Mbit/s (12 m), 100 kbit/s (1200 m) • Max. 1200 m • Standard does not define protocol and pins

  18. Differential signaling source: www.root.cz source: www.root.cz

  19. RS-422 Log. 0: VA – VB ≥ +0.2 V Log. 1: VA – VB ≤ -0.2 V source: www.scantec.de source: meteosat.pessac.free.fr

  20. RS-485 • ANSI/TIA/EIA-485 (1998) • Uses differential signaling • 32 transmitter + 32 receivers • 10 Mbit/s (12 m), 100 kbit/s (1200 m) • Max. 1200 m • Standard does not define protocol and pins

  21. RS-485 signaling Log. 0: VA – VB ≥ +0.2 V Log. 1: VA – VB ≤ -0.2 V Source: www.consultants-online.co.za source: www.sealevel.com

  22. RS-485 devices Internally each node can have a transmitter and receiver, they are switched into high-impedance mode when not used Source: www.root.cz

  23. Half duplex source: www.alciro.org

  24. full duplex source: www.alciro.org

  25. Grounding source: hw.cz

  26. Maximal speed source: hw.cz

  27. RS-422 vs. RS-485 source: hw.cz

  28. USB • Universal serial bus (1995) • Differential signaling (DATA + , DATA -) + power source: www.se7ensins.com source: en.wikipedia.org

  29. USB specifications • Max. 127 devices • Superspeed – 5 Gbit/s (USB 3.0 - 2008) • High Speed - 480Mbits/s (USB 2.0 - 1999) • Full Speed - 12Mbits/s • Low Speed - 1.5Mbits/s

  30. USB signaling • Uses NRZI (Non Return to Zero Invert) signaling D+ device host D- • Differential „1“: D+ > 2.8 V, D- < 0.3V • Differential „0“: D-> 2.8 V, D+ < 0.3V • Differential „1“: D+ greaterthanD- • Differential „0“: D+ lessthanD-

  31. USB signaling source: www.tek.com

  32. Speed identification • Full speed device source: www.beyondlogic.org

  33. Speed identification • Full speed device source: www.beyondlogic.org

  34. Non Return to Zero Invertsignaling • "One" is represented by a transition of the physical level. • "Zero" has no transition. source: www.jbmelectronics.com source: en.wikipedia.org

  35. Ethernet – physicallayer • Standard IEEE 802.3 • Max. length 100m • 3 Mbit/s to 100 Gbit/s • Differential signaling • Signals TX+, TX-, RX+, RX- source: techpubs.sgi.com

  36. Ethernet – physicallayer Logic levels (10BaseT - output) • Log. 1 > +0.7 V • Log. 0< -0.7 V source: hw-server.com source: www.interfacebus.com source: sigalrm.blogspot.com

  37. Ethernet – Manchester encoding • Encoding helps clock recovery source: en.wikipedia.org

  38. Ethernet – physicallayer Ethernet data, showing MLT-3 encoding of bits. (used in e.g. 100BASE-TX) source: flickr.com

  39. Ethernet – Data Link Layer - frame synchronization source: communities.netapp.com

  40. Ethernet – Data Link Layer - frame addresses source: communities.netapp.com

  41. Ethernet – Data Link Layer - frame identifies what higher-level network protocol is being carried in the frame (example: TCP/IP) source: communities.netapp.com

  42. Ethernet – Data Link Layer - frame data source: communities.netapp.com

  43. Ethernet – Data Link Layer - frame Control checksum Cyclic redundancy check source: communities.netapp.com

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