helpful for MSBTE Diploma students

1. USB (Universal Serial Bus)
1
Original logo
The basic USB trident logo
A flash drive, a typical USB
mass-storage device.
eSATAp (eSATA/USB) combo port is compatible
with USB devices

2. 2
Series "A" plug and receptacle.
Types of USB connectors left to right:
• male Micro B
• male Mini B (8-pin)
• male Mini B (5-pin)
• female standard A
• male standard A
• male standard B
Pin configuration of the USB connectors
Standard A/B, viewed from face of plug

3. RS232
• A Recommended Standard (RS) interface
developed by The Electronics Industrial
Association (EIA).
• Uses Asynchronous & serial communication
method.
• A standard for serial binary data signal
connecting between DTE (Data terminal
Equipment) & DCE(Data Communication
Equipment).
• The standards has been renamed, variously
known as RS232, EIA232, TIA232 & current
version TIA232F.

4. • RS232 expect a MODEM to be connected to both
Transmitting & receiving end.
• COMPUTER- DTE(Data terminal Equipment)
• MODEM- DCE(Data Communication Equipment)
• DTE & DEC are linked via a cable.
• DTE has a 25 pin D-type male connector.
• DEC has 25 pin D-type female connector.

6. Voltage levels ofRS232
• Uses two voltage levels, Logic 1 & Logic 0.
• Logic 1- Marking State or Quiescent State.
Indicates Negative(-) Level. (OFF)
• Logic 0- Space state. Indicates Positive (+)
level.(ON)
• Valid signals are 3 to 15 Volts.
• The range near 0V is not a valid RS-232
level.
• Maximum open circuit voltage will be 25V.

7. Data Signal
Level Transmitter Receiver
Logic 0 (Spaces) +5V to +15V +3V to +25V
Logic 1 (Marks) -5V to -15V -3V to -25V
Undefined -3 V to +3V
Control Signal
Signals Driver Terminator
OFF (Marks) -5V to -15V -3V to -25V
ON (Spaces) +5V to +15V +3V to +25V

8. Signal Description…..
• CD (Carrier Detect or Carrier Data Detect)-
– Used by the computer to know that the modem
connected to the serial port has made proper
connection with modem on the other side.
• RxD (Receive Data)-
– Used by the device connected to the serial port to
send data to the computer OR data send from DCE to
DTE.
• TxD (Transmit Data)-
– Used by the computer to send data to a device
connected to the Serial port Or Data sent from DTE to
DCE.

9. • DTR (Data Terminal Ready)-
– Send from computer to the device connected
to the serial port to inform that computer is
ready for communication.
• DSR (Data Set Ready)-
– Send from device connected to the serial port
to the computer to inform that device is
ready for communication.
• GND (Signal Ground)-
– Provides the necessary return path for both
the Data Signal & Hand shaking signal..

10. • RTS (Request To Send)-
– Send by the computer after receiving Clear to
Send (CTS) to the device connected to the serial
port.
– Informs that Computer is ready for Data
Transmission.
• CTS (Clear To Send)-
– Used by the device connected to the serial port to
inform the computer that computer can start the
Data transmission.

11. • RI (Ring Indicator)-
– Used by the device connected to the Serial port to
inform the computer that it has detected a ringing
Voltage on the telephone Line.
– This Signal is used by a MODEM connected to the
Serial port to inform the Computer that someone
is calling the MODEM.

12. A Communication Session/ Sequence
of Events in RS 232 Communication.

13. • Check all hardware at both end i.e. Computer
(DTE) & Serial device (DCE) must be properly
connected using proper cable, and switched
switched ON.
• Both the Computer & Serial device must be
configured to use same data, communication
protocol.
i.e. Speed, number of start, data & stop bit
and the parity…

14. • Start the communication process computer
will make high the DTR signal and the device
will make the DSR signal high.
• If the device is a MODEM than if any
telephone call comes the MODEM will send RI
signal to the computer.
• Once the MODEM bus made proper
connection with the calling phone, it will send
CD signal to the computer.
• Next computer will make high the RTS Signal
& the MODEM or device connected to the
Serial interface will make the CTS Signal High.

15. • A slow serial device may can’t receive
characters as fast as computer is sending
them, then the device will send CTS low to
indicate the computer to stop data
transmission for some time. After that it will
send CTS positive Signal.
• Same case for slow computer, but the signal is
RTS.

16. NULL MODEM (serial port in PC)
TxD
TxDRxD
RxD
RTS
RTS
CTS
CTS
DSR
DSR DTR
DTR
SG SG
Computer
(DCE)
Terminal
(DTE)
2
3
4
5
6
7
20
2
3
4
5
20
7
6
Null MODEM Links in PC

17. • A method of connecting Two DTEs (Computer,
printer etc.) directly using RS232 cable.
• Originally RS232 standard only defined the
connection of DTEs with DCEs i.e. MODEMs..
• With NULL MODEM Transmit & Receive lines are
Crosslinked….
• Purpose is to permit two RS232 DTE devices to
communicate with each other without MODEMS
i.e. DCEs.
• Can be used for equipment, such as terminal,
printer, mouse, optical scanner, bar code reader,
voice synthesizer, OMR, OCR etc…..

18. Data Lines
STROBE (Take Data)
ACK Give Data
Busy
PE (No Paper)
ERROR (Fault)
SLCT IN (Enable Interface)
SLCT (Selected)
AUTO FEED XT (Hardware Line Feed)
INIT (RESET)
Ground
Print
Controller
(Computer side)
Printer
Side
Signals in Centronics Interface

19. Signals From PC to Printer
• STROBE-
– The printer takes Data when this signal is Low.
• INIT-
– When Low, printer resets its electronic logic and
clear the printer Buffer.
• SLCTIN-
– An interface enable signal, when Low, the printer
responds to Signal from the controller.
• AUTO FEED XT-
– A Hardware line feed, after printing every line by
printer.

20. Signals from Printer to PC
• ACK -
– Acknowledgement for STROBE signal from PC.
– When active indicate that printer has received
data sent by PC & is ready to accept next data
byte.
• BUSY-
– When High indicate the printer is busy & can not
receive the data.
1. On receiving STROBE active.
2. During printing operation.
3. When the printer is in offline state.
4. When the printer senses some error condition.

21. • PE-
– When High, it indicates that there is no proper in the
Printer.
• SLCT-
– Indicates that the printer is selected & Logically connected
to the PC.
• ERROR-
– Indicates Error conditions in the Printer.
– Reasons –
1. Mechanical or electronic Fault.
2. The printer is in Offline state.
3. No paper in the Printer.

22. Firewire (IEEE 1394)
• Introduced by Apple PC in 1995 &
subsequently standardized by IEEE 1394.
• A serial interface for verity of high speed
peripherals including multimedia devices.
• Offers High speed communication &
isochronous real-time data services.
• Adopted as the High Definition Audio-Video
Network Alliance (HANA) standard
connection interface for A/ V components
control.

24. Features of Firewirw (IEEE 1394)
• Hot pluggability & Plug & play use.
• Can connect 63 peripherals in Acyclic topology.
• Allows peer-to-peer device communication.
• Supports multiple hosts per bus.
• Uses SIX-wire cable, flexible than SCSI.
• Can supply 45W power per port at up to 30 V.
• Data transfer rates- 100, 200, 300, 400Mbits/s.
• Modes referred as S100, S200, S300, S400.

25. • Cable length is limited to 4.5m (15ft), 16
cables can be daisy chained using active
repeaters.
• Snap connection- no need of device ID,
Jumpers, DIP Switches, terminators etc…
• Power sourcing.
• Isochronous Data transfer.
• DMA support.

26. Firewire Vs USB
Sr. No. Points Firewire USB
1 PC-host require NO YES
2 Max. Number of devices 63 127
3 Hot Swappable Yes Yes
4 Max. Cable Length 4.5 meters 5 meters
5 Transfer Rate 400 Mbps/ 800 Mbps 12 Mbps/ 480 mbps
6 Device supported DV camcorders Higher
digital cameras HDTV,
Set-top boxes, High-
speed drives, high-
resolution scanners,
Electronic Musical
Instrument.
Keyboard, mice,
Joysticks, Cameras,
MODEMs, Scanners,
Set-top boxes,
mobiles, etc….