Communication lines

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

OSI model Open Systems Interconnection (OSI) model (ISO/IEC ) Source: homepages.uel.ac.ukhomepages.uel.ac.uk Physical layer – Transmits raw bit stream over physical cable IEEE 802, RS232, RS422, RS485, I 2 C, SPI,…

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

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

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 TXRX Log. 0 : +5 to +15 V Log. 1 : -15 to -5 V Log. 0 : > +3 V Log. 1 : < -3 V Noise immunity: min. 2 V

RS232 (EIA232) Length RS-232-C = 15 m RS-232-F defines max. load capacity 2500 pF TXRX C RX ~20 pF CMCM signal shield CSCS CSCS

RS232 - Cable capacity C S ~ 0,5 C M unshielded cable C S ~ 2 C M shielded cable C RX ~20 pF CMCM signal shield CSCS CSCS Max. length: L max = 2500 / C total C total = C M + C S e.g. Belden 1700A TP: 78,7 Ω/km, 45,9 pF/m

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

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

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

RS232 - Communication speed RS-232-F standard defines speeds: 50,75,110,150,300,600,1200,2400,4800,9600,19200 bit/s Common speeds above standard definition: 28800, 38400, 57600, bit/s Higher speed = lower distance Baud rate [Bd]Max length [ft]Max length [m] source:

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

RS232 - Connectors source: 9 pin

RS232 - Connectors source: fjkraan.home.xs4all.nlfjkraan.home.xs4all.nl 25 pin source:

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

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 m Standard does not define protocol and pins

Differential signaling source: source:

RS-422 source: meteosat.pessac.free.frmeteosat.pessac.free.fr source: Log. 0: V A – V B ≥ +0.2 V Log. 1: V A – V B ≤ -0.2 V

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 m Standard does not define protocol and pins

RS-485 signaling Source: source: Log. 0: V A – V B ≥ +0.2 V Log. 1: V A – V B ≤ -0.2 V

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

source: Half duplex

source: full duplex

Grounding source: hw.czhw.cz

Maximal speed source: hw.czhw.cz

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

USB Universal serial bus (1995) Differential signaling (DATA +, DATA -) + power source: source: en.wikipedia.orgen.wikipedia.org

USB specifications Max. 127 devices Superspeed – 5 Gbit/s (USB ) High Speed - 480Mbits/s (USB ) Full Speed - 12Mbits/s Low Speed - 1.5Mbits/s

USB signaling Uses NRZI (Non Return to Zero Invert) signaling host device Differential „1“: D+ greater than D- Differential „0“: D+ less than D- D+ D- Differential „1“: D+ > 2.8 V, D- < 0.3V Differential „0“: D- > 2.8 V, D+ < 0.3V

USB signaling source:

Speed identification Full speed device source:

Speed identification Full speed device source:

Non Return to Zero Invert signaling "One" is represented by a transition of the physical level. "Zero" has no transition. source: en.wikipedia.orgen.wikipedia.org source:

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

Ethernet – physical layer Logic levels (10BaseT - output) Log. 1 > +0.7 V Log. 0 < -0.7 V source: hw-server.comhw-server.com source: sigalrm.blogspot.comsigalrm.blogspot.com source:

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

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

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

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

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

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

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