Ports Connector

Ports & Connectors The Ports and Connectors are basically the connection points through which we connect various types of I / O devices externally or internally with the system. The external I / O devices are keyboard, mouse, printer, scanner and WEB camera etc. Whereas the internal I / O devices are Floppy disk drives, Hard disk drives and CD - ROM etc. These ports and connectors are designed differently in order to avoid any kind of damage to the device or the system electronic sections as the user of the system could be a non – technical (electronics) person and might not be able to understand the complexity of connectivity of the devices with the system. Connecting wrong device with the wrong connection points may lead to partially or completely damage to the device or the electronic section controlling its functioning or to both. Types of Ports and connectors These ports and connectors could be classified in to two main categories on the basis of their placement in the system and the use. One of these two ports is called External Ports and Connector and the other as Internal Port and Connector. External Port and Connectors These ports could be seen on the back of the CPU cabinet. These ports and connectors are used to connect the system and a device together, using a connecting cable so that they can communicate with each other. We can see various types of ports and connectors on the back side of the cabinet; each has a different size and shape.

1. Power Connector The power connector is given on the Power Supply unit of the system. There maybe one or two connectors. This depends on the discretion of the manufacturer. These connector are also of two different shapes, Male and Female type. The male type is used to connect Mains cord with the system to give the AC 220V as input supply and the female type of power connector (if available) is used to connect Monitor to give AC 220V input supply voltage.

2. Keyboard Port / Connector [email protected] 09889907375

This port is used to connect keyboard with the motherboard. There are two types of keyboard port / connectors used in the system.

(A) 5 Pin - Din socket [deustch industries norms] The 5 Pin - din Socket was widely used in earlier motherboards to connect the keyboard with the motherboard. These connectors are also known as AT keyboard connectors. This connector had 5 pins and was bigger in size. Standard color – Black. It is also called DIN 5 Connector. (B) PS/2 Type This connector was introduced by IBM in its PS/2 model and later on gained popularity among other clone company based systems also. This connector is smaller in size and has 6 pins. This connector is similar to the PS/2 Mouse connector but generally the keyboard connector is located below the PS/2 mouse connector and is near to the motherboard PCB. Standard color – violet.

3. Mouse Port [PS/2 Type] Its color is green. It is present in ATX Motherboard.

4. Serial Port (COM1 / COM2) This port is used to connect serial mouse or any serial communication device such as Serial Printer or External Modem with the system. There are two types of serial connector used in the system. The 9 Pin D – Type connector and 25 Pin D - Type connector. Both the types of connectors are known as Male connectors as both of them have 9 or 25 pins respectively. The 25 Pin D Type connectors are now obselete, hence not used in newer version of motherboards starting from Pentium - II. It is also called COM port. Standard color – Green/Black. Speed – 9.6 kbps- 115kbps Use for Mouse, Printer. 5. Parallel Ports Its standard color is pink. Use for Printer (Dot matrix).This port has 25 pins to connect devices such as printers, scanners, external hard disk drives etc. This port is also known as printer port because this port is mainly used for connecting printer supporting parallel interface. The 25 pin connector has 8 pins dedicated for data lines that means 8 bit data could be transmitted from one section to the other at a time. This port uses a female type 25 pin D type connector and looks like the figure given below: [email protected] 09889907375

There are different types of parallel ports used in the system. The difference between them is their capability to transmit the data and other signals. These different types of parallel ports are as under: Unidirectional This port transmits data in one direction at a time that means either sending data or receiving data at a time. SPP It is known as Standard Parallel Port. This enables bidirectional data communication between the system and device simultaneously at a time. That means the device can send the data while receiving at the same time. EPP It is known as Enhanced Parallel Port. This provides data transfer speed of 500 kb to 2 Mb of data per second between the system and the device. This port is used for attaching external storage devices to the system or scanners. ECP It is known as Enhanced Capabilities Port. This provides data communication speed between the system and the device. 6. USB Port The USB is known as Universal Serial BUS. The BUS through which number of devices could be connected with the system. This port was developed by a group of some leading IT organizations like Intel Corp., Microsoft, HP, DELL etc. This port was developed in order to attach new devices with the system to use system resources when ever connected and required because in earlier Pc’s there was a limitation of devices to be connected with the system and to which the system hardware recognizes but with the introduction of new devices such as WEB Camera and storage devices like Pen drive the need to recognize these devices and to allow a faster data transmission was required. This requirement was fulfilled by a dedicated port known as USB port. In order to easily identify this port from other ports and connectors USB port is given a different design. The figure below shows different types of USB ports. USB carries data at the rate of 12 megabits per second, which is sufficient for "medium to low-speed peripherals". This broad category includes Mobiles, digital cameras, modems, keyboards, mice, digital joysticks, some CD-ROM drives, tape and floppy drives, digital scanners and specialty printers. USB's data rate also accommodates a whole new generation of peripherals, including MPEG-2 video-base products. Computertelephony integration is expected to be a big growth area for PCs, and USB can provide an interface for Integrated Services Digital Network (ISDN). Technically, up to 127 individual USB peripherals could be connected at a time. It is hot swappable. Win 95, Win NT, and UNIX are not compatible with USB Port.

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7. Monitor Port The monitor port is used to connect monitor with the system. Earlier systems based on CGA (Color Graphic Adapter), MDA (Monochrome Display Adapter) and EGA (Enhanced Graphic Adapter) display cards had 9 Pin D Type connector but the systems now a days are based on VGA (Video Graphic Array) and AGP display cards uses 15 Pin D-Type female connector (port). The monitor is given some basic signals such as Red colour info, Green colour info, Blue colour info, and Intensity, Vertical and Horizontal Sync signals through this port to produce the picture on the screen. Earlier this port was available on display card (as used in the system) but now, this port is placed on the motherboard itself. The figure below shows the Monitor Port and the Monitor interface cable connector. This connector is used to connect the VGA port connected in the slot area of the cabinet to the motherboard based display controller section. These connectors have 15 or 16 pins and are marked on the motherboard as VGA. 7. Network Port [email protected] 09889907375

This port is generally given on the Network Interface Card (NIC), which is now available on motherboards also. This port is used to connect network cable segment with the system to enable data flow in the network environment. Generally two types of ports are used for network cable segment, one BNC connector and other RJ 45 or UTP connector. Today’s motherboards have RJ 45 connectors connected on it and could be found in the back side of the system in between other ports and connectors. 8. Sound Port This port was earlier the part of the sound card but now; built on the motherboard therefore this port is also provided on the rear side of the motherboard along with the other ports and connectors. The sound port has three points to connect MIC, Speaker and any sound input device in Line in. These ports are now provided with a colour rings in order to easy identification. The pink colour ring is for MIC, the Green is to connect speaker and the Blue ring is to connect Line in device such as tape recorder, MIDI device etc. Generally the top connector ring is for Line in, the center connector ring is for speaker and the bottom connector (near the motherboard PCB) is used to connect MIC. This colour ring codes are however used in general but it could change from manufacturer to manufacturer basis. Internal Connectors The internal connectors are found on the motherboard or any adapter cards. These connectors are used to connect respective devices as per the controlling sections. Now a days most of these connectors are placed on the motherboards itself only few connectors are found on any adapter cards since today’s system uses a integrated (single board technology) motherboards which not only has important sections but also has controllers earlier used as an adapter card. These connectors and their shapes are as under: 1. HDD Connector [email protected] 09889907375

This connector is used to connect hard disk drives with the motherboard based its controlling section. There are physically two HDD connectors on the motherboard. The first one is known as Primary HDD connector or IDE 1 and the second one is known as Secondary HDD connector or IDE 2. Some times these connectors are also termed as Primary HDD and Secondary HDD. Each connector has 40 pins and notch on one of the side wall of the connector. This notch helps to connect the IDE interface cable used to connect hard disk and the controlling section in correct way as connecting the cable in wrong way may damage the HDD or controller or both. 2. FDD Connector This connector is used to connect floppy disk drives with the system and to its controlling section. There is only one connector given on the motherboard to connect floppy disk drive(s). This connector looks similar to the HDD Connector but is slightly smaller in size as it has only 34 pins. This connector like HDD Connector also has a notch in the middle of one of its wall. 3. Power Connector This connector is used to connect wire / connectors coming from power supply of the system. There are generally three types of power connectors used in the motherboard. Depending of the motherboards supply requirements and support features, there might be one of these three connectors or all of them connected on the motherboard. These power connectors are as under: (i) AT Power Connector The AT power connector was used in the system from PC - XT to AT systems based on Pentium II and some Pentium III processor. AT power supplies use a pair of connectors called P8 and P9 to provide power to the AT motherboard. Each of these connectors has a row of teeth along one side and a small guide on the opposite side that help to hold the connection in place, Figure below shows the AT power plug on the motherboard. P8 and P9 power connectors are faced (that is, they have a front and a back), to avoid wrong connectivity of the connectors. Sometimes the small keys on P8 and P9 require angling the connectors in before snapping them down. Figure shows a technician angling in the P8 and P9 connectors. In order to avoid wrong connection and actual placement of P8 and P9 connectors the black wires of both P8 and P9 connectors should face each other and then slided. The wrong placement of P8 and P9 connectors could lead to damage motherboard circuitry. Red wire 12V and yellow wire 5V current supply.

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ATX Power Connector The ATX stands for Advance Technology - Extended. This connector was introduced from the systems based on Pentium II or compatible processor and soon it became popular in almost every systems based on Pentium II / III / IV or compatible systems. Like motherboards there is different form factors used in the power supplies also. The earlier supply known as AT Power supply (SMPS) was a manually operated power supply whereas the ATX power supply is a pulse driven power supply which means the power supply will release or stop the supply of power from SMPS on getting a pulse. Due to this feature system could be started automatically on accessing via LAN or on receiving any call on phone line.

Another major factor of difference between the two types of power supplies is their output voltage levels. The AT power supply generates a constant +5V, + 12 V, - 5 V and - 12 V output voltages and the ATX power supply generates + 3.3 V output voltage along with the voltages as generated in AT power supplies. There are two types of connectors used in ATX power supplies, the first one is known as 20 Pin Molex connector and the second one is known as ATX 12 V connector. ATX use a single P1 power connector instead of P8 & P9. Peripheral power: Device like mass storage and media drives, hard drives, floppy disk drive, ZIP drive, CD ROM drive and Fan also draw power directly from the PC power supply. AT and ATX power supplies both have the Molex and mini connector used by the device.

Front Panel Connectors The front panel connectors are basically some indicator and control switch connections. These connectors includes indicators like HDD function LED, Power LED and control switches like Power On / Off switch and Reset switch connections. The wires coming from front panel also known as bezel are connected with these connectors. The figure below shows these connectors. The connection pins are marked on the motherboard PCB for the wire to be attached with them or some times a layout is provided with the motherboard either in the form of a user manual or a sticker showing the placement of the connectors. Apart from these connectors mentioned earlier [email protected] 09889907375

some other type of connectors are also used mainly in the Pentium I / II and III category systems. These connectors are used to connect the ports with the motherboards. 5. IEEE 1394 Port IEEE 1394 is a very fast standard that supports of up to 400 (in 1394a) and 800Mbps (in 1394b). Products supporting the 1394 standard go under different names, depending on the company. Apple, which originally developed the technology, uses the trademarked name FireWire. Other companies use other names, such as i.link and Lynx, to describe their 1394 products. A single 1394 can be used to connect up 63 external devices. In addition to its high speed, 1394 also supports data, delivering data at a guaranteed rate. This makes it ideal for devices that need to transfer high levels of data, such as devices. Although extremely fast and flexible, 1394 is also expensive. Like 1394 supports both and, and also provides power to peripheral devices.

Motherboard Resources In computer system every device requires a medium to communicate, to inform about itself and proper information about where to transmit its data. In order to have proper communication between devices in the form of signals certain signal lines are required which we can term as motherboard resources or in other words system resources. These system resources help in sending or receiving the information (data) from one section / device to the proper destination.

Interrupt Request Query The Interrupt Request Query is also termed in its short form as IRQ channels or hardware interrupts. These IRQ’s are used by various devices to signal the processor that the device wants to communicate and its request must be fulfilled. These interrupt channels are represented by wires on the motherboard and in the expansion slots. When a particular interrupt is invoked, a special routine takes over the system, which first saves all the [email protected] 09889907375

CPU register contents in a stack (register inside the CPU) and then directs the system to the interrupt vector table. This vector table contains a list of memory addresses that correspond to the interrupt channels and with the help of this vector table CPU identifies which device wants its attention. Through the use of interrupts, the system can respond to external events in a timely fashion. Each time for example, the serial port presents a byte to the system; an interrupt is generated to ensure that the system reads that byte before another comes in. These hardware interrupts are prioritized by their number, the highest - priority interrupts have the lowest numbers. Higher priority interrupts take precedence over lower – priority interrupts by interrupting them. As a result, several interrupts can occur in the system concurrently. In general each I / O device is assigned a unique IRQ and if any two device uses the same IRQ at the same time then a resource conflict takes place and as a result the system assigns the IRQ on the priority basis. The earlier XT systems (based on 8088 processor) had 8 IRQ’s and the new generation AT systems (systems based on 80286 onward processor) has 16 IRQ’s. The list of IRQ number and its assigned device is given below: DMA Channels The DMA Channels are basically known as Direct Memory Access Channels. These channels are used by high - speed communication devices that must transact the information at a high speed. The devices which uses DMA channel could access the memory directly without the association of processor. A Serial or Parallel port does not use a DMA channel, but a network adapter card does, likewise some of the newer type of hard disk drives also supports DMA. DMA channel could be shared if the devices connected with the system are not of the type that would need DMA channels simultaneously. Like IRQ, DMA channels are different for PC - XT and AT systems. The DMA channels for PC - XT systems are known as 8 bit ISA BUS DMA channel and for PC - AT systems it is known as 16 bit ISA DMA channel.

I / O Address I / O Address is also known as I /O Port Address or Memory Address. A personal computer may transfer data from disk to CPU, from CPU to memory, or from memory to the display adapter. A PC cannot afford to have separate circuits between every pair of devices. The I / O address is a hexadecimal number (the address) that identifies a particular device or memory location. The computer chips watch the address wires and respond when their identifying number is transmitted. They then transfer data on the other wires known as data bus. Each I/O device connected to the computer is mapped to a unique pattern of 16 ones and zeros known as I/O (Input/Output) address such as 0000000111110000. These addresses are assigned to every I/O port on the computer, including USB, Firewire, Ethernet, VGA ports. Having a unique address assigned to each port allows the computer to easily recognize and locate devices attached to the motherboard be it a keyboard, mouse, display [email protected] 09889907375

controller, printer, or any other device. The computer can locate it by its I/O address. There are three basic rules which apply to I /O addresses. 1. All devices must have a unique I / O address. 2. All devices may use more than one I / O address. 3. Once a unique I / O address is assigned to any device, no other device can use that address. The list given below shows I / O addresses range and the device using them.

PnP PnP stands for Plug and Play features. This feature was introduced from Pentium – I category systems. In early Pc’s new devices such as sound card or LAN cards, when added to the system required manual configuring to attach them with the system hardware which included installing the card in the expansion slot, installation of respective software and resolving resource conflict if any manually to make them working. The plug and play feature introduced from Pentium - I onward and Windows 98 operating system enabled the system to automatically identify new addition of any hardware devices, assign them their related system resources such as IRQ, DMA channels and I / O port address along with the software driver (if available in the database of the operating system) and start the functioning of the newly added device. Incase if the operating system does not have any compatible device driver software then it prompts the user to install that software from the disk provided by the manufacturer of the device. This feature of automatic configuring the device on connecting with the hardware is termed as Plug and Play. In order to activate this feature the device to be connected with the system should also be designed and support the Plug and Play standards. For PnP to work properly, the PC needs three items: 1. The BIOS of the system motherboard should be PnP BIOS. This could be identified by closely monitoring the screen during the boot process as given in the figure. 2. The system should have a PnP supporting operating system such as Windows 9x / ME, Windows 2000 / XP etc. The older operating system such as DOS does not support PnP feature. 3. The device to be added in the system should be a PnP device be it a sound card, display controller, network interface card or modem and even a printer. All the devices currently available in the market are usually PnP devices and generally mentioned on them.

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