Processor to Network Interface
Network Interface Card (NIC) is an expansion board inserted into a computer so that the
computer can be connected to a network. Most NICs are designed for a particular type of
network, protocol, and media although some can serve multiple networks.
Performs two crucial tasks
1. Establishes and manages computer’s network connection.
2. Translates data into signals for outgoing messages and translates signals for
incoming messages.
Most computers use parallel data lines, called bus, to send data between CPU and adapter
Cards. Most networking media transmits data in single line, called serial transmission.
NIC translates parallel into serial for outgoing messages and serial into parallel for
incoming messages
A 'network interface controller (NIC)' is a hardware device that handles an interface to a
computer network and allows a network-capable device to access that network. The NIC
has a ROM chip that contains a unique number, the media access control (MAC) Address
that is permanent. The MAC address identifies the device uniquely on the LAN.
Sometimes the words 'controller' and 'card' are used interchangeably when talking about
networking because the most common NIC is the network interface card. Although 'card'
is more commonly used, it is less encompassing. The 'controller' may take the form of a
network card that is installed inside a computer, or it may refer to an embedded
component as part of a computer motherboard, a router, expansion card, printer interface
or a USB device.
A MAC address is a 48-bit network hardware identifier that is permanently set on a ROM
chip on the NIC to identify that device on the network. The first 24-bit field is called the
Organizationally Unique Identifier (OUI) and is largely manufacturer-specific and the
remaining bits are specific to each chip. There are four techniques used to transfer data,
the NIC may use one or more of these techniques.
•Polling is where the microprocessor examines the status of the peripheral under
program control.
• Programmed I/O is where the microprocessor alerts the designated peripheral by
applying its address to the system's address bus.
• Interrupt-driven I/O is where the peripheral alerts the microprocessor that it's
ready to transfer data.
• DMA is where an intelligent peripheral assumes control of the system bus to
access memory directly. This removes load from the CPU but requires a separate
processor on the card.