rs232 serial and parallel interfaces. comsats institute of information technology, wah cantt.2 what...

RS232 Serial and RS232 Serial and Parallel Parallel InterfacesInterfaces

COMSATS Institute of Information Technology, Wah Cantt. 2

What Is a Interface?What Is a Interface?

The point of interaction or The point of interaction or communication between a communication between a computer and any other computer and any other entity, such as a printer or entity, such as a printer or human operatorhuman operator..


Types of InterfacesTypes of Interfaces

RS232 nine pin serial portRS232 nine pin serial port Parallel portParallel port USB portUSB port SCSI portSCSI port IEEE 1394IEEE 1394 PCI cards, etc.PCI cards, etc.


RS232 9pin Serial PortRS232 9pin Serial Port Has existed for Has existed for

approximately 20 approximately 20 yearsyears

RS232 stands for RS232 stands for Recommended Recommended Standard 232 CStandard 232 C

Used mostly for Used mostly for devices that transmit devices that transmit or receive small or receive small amounts of dataamounts of data


What Does Serial Mean?What Does Serial Mean?

The name 'serial' comes from the The name 'serial' comes from the way that a serial port 'serializes' way that a serial port 'serializes' data. That is, it takes a byte of data data. That is, it takes a byte of data and transmits the 8 bits in the byte and transmits the 8 bits in the byte one bit at a time.one bit at a time.


How Does It Work?How Does It Work?011011101101110000 00 00 00 00 00

00

00

00

11 11 11 11 11 11

11

11

11


Facts About the RS232 Facts About the RS232 PortPort

Data throughput rate of 115KbpsData throughput rate of 115Kbps Most computers have one or two RS232 Most computers have one or two RS232

ports built in to the motherboardports built in to the motherboard More ports can be added by adding an More ports can be added by adding an

adapter card to the computer; These adapter card to the computer; These cards again add one or two extra portscards again add one or two extra ports

All RS232 devices need to have a All RS232 devices need to have a device driver installed on the computer device driver installed on the computer to operate correctlyto operate correctly


RS232 SummaryRS232 Summary

In general the RS232 interface is In general the RS232 interface is a fairly slow and complex way to a fairly slow and complex way to connect devices to a computer. connect devices to a computer. The lack of protocol and The lack of protocol and configuration standards for the configuration standards for the interface means that users must interface means that users must manually configure the port for manually configure the port for each new device added.each new device added.


The Parallel PortThe Parallel Port

Developed by IBM Developed by IBM to connect PC to a to connect PC to a printerprinter

Probably most Probably most common form of common form of port usedport used


Types Parallel PortsTypes Parallel Ports Uni- DirectionalUni- Directional Bi-DirectionalBi-Directional


What Does Parallel Mean?What Does Parallel Mean?

Of or relating to the Of or relating to the simultaneous transmission of simultaneous transmission of all the bits of a byte over all the bits of a byte over separate wires:separate wires: a parallel part; a parallel part; a parallel printer.a parallel printer.


How Does It Work?How Does It Work?

0110111011011100

0011110011111100

0011110011111100

0011110011111100

0011110011111100 01101110110111

0001101110110111000110111011011100


Facts About a Parallel PortFacts About a Parallel Port

The specification allows up to 2MbpsThe specification allows up to 2Mbps The specification allows up to a 10 meter The specification allows up to a 10 meter

cablecable Most PC’s come with one or two parallel Most PC’s come with one or two parallel

ports, as with a serial port, more can be ports, as with a serial port, more can be added if required (1 or 2 only)added if required (1 or 2 only)

All devices require a device driver which is All devices require a device driver which is usually provided by device manufacturerusually provided by device manufacturer


Parallel Port PinsParallel Port Pins

1 2 3 4 5 6 7 8 9 10 11 12 13

14 15 16 17 18 19 20 21 22 23 24 25

DB-25 Male Connector


Parallel Port Pin Parallel Port Pin ConfigurationConfiguration

10 11 12 13

15

5 Status Pins5 Status Pins

2 3 4 5 6 7 8 9

8 Data Pins8 Data Pins

1

14 16 17

4 Control Pins4 Control Pins

18 19 20 21 22 23 24 25

8 Ground Pins8 Ground Pins

DB-25 Male Connector


Pin Assignment & Pin Assignment & DescriptionsDescriptions

1.1. StrobeStrobe PC PC OutputOutput

2.2. Data 0Data 0 PC PC OutputOutput








10.10. ACK (Acknowledgment)ACK (Acknowledgment) PC PC InputInput

11.11. BusyBusy PC PC InputInput

12.12. Paper EmptyPaper Empty PC PC InputInput

13.13. SelectSelect PC PC InputInput

14.14. Auto FeedAuto Feed PC PC OutputOutput

15.15. ErrorError PC PC InputInput

16.16. Initialize PrinterInitialize Printer PC PC OutputOutput

17.17. Select InputSelect Input PC PC OutputOutput


Simple LEDs Driving Simple LEDs Driving CircuitCircuit

10 11 12 13

15

2 3 4 5 6 7 8 91

14 16 17 18 19 20 21 22 23 24 25

Grounding Pins

100 Ohm Resistance

or Deponds on LEDs3 Volts LEDs

Cathode

Anode


LEDs Driving Circuit - LEDs Driving Circuit - ExampleExample

1 1 0 0 0 1 0 1

Grounding Pins

100 Ohm Resistance

or Deponds on LEDs3 Volts LEDs

Cathode

Anode


Simple Example ProgramSimple Example Program

#include <dos.h> // Include header file

#define DATA 0x378 // Base address of Data Pins#define STATUS DATA+1 // Status address of Status Pins#define CONTROL DATA+2 // Control address of Control Pins

void main(void){ outportb(DATA, 0x00); // Turn all the LEDs off delay(1000);

outportb(DATA, 0x01); // Turn the 1st LED on delay(1000);}

rs232 serial and parallel interfaces. comsats institute of information technology, wah cantt.2 what...

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