COMPUTER INTERFACING

By Aravin Amirthalingam, Steve Ho, and Justin Wong

INTERFACES

Interfaces are necessary in society because they allow information to be directed between two sources. Interface within computer systems involves the communication between the CPU of a computer with outside sources. Interfaces accomplish this by taking messages sent from the outside sources, translating them, and sending them to the CPU. Interfaces can also work backwards and send information from the CPU back to the outside source.

HOW IT WORKS

The outside sources sends a message to the CPU which travels to a driver. The driver translates the message into a language that the computer's operating system can understand. The O/S interprets the message and sends it to teh CPU, which then responds to the message. If a message is sent back it takes a reverse course.

WHY INTERFACES MUST BE DESIGNED AT ALL LEVELS AND ENVIRONMENT

If one level or environment is poorly connected, it could corrupt the data passing through the interface and thus the whole interface would be essentially useless. The interface is only as strong as its weakest component.

EXAMPLES OF INTERFACE

1. INTERFACING BETWEEN HUMANS AND COMPUTERS - to allow us to communicate to the computer in a language we understand (eg. operating system, character sets)

2. MASTER/SLAVE INTERFACES - are between two components in which one controls the other or has priority over the other (eg. the master ha rd disk drive is the one from which you load the operating system and is thus usually higher performing than the second, slave drive, and is of higher importance)

3. DIRECT MEMORY ACCESS (DMA) INTERFACES - transfers data from a storage device directly to memory without passing through a processor (eg. DMA hard disks perform faster than non-DMA)

4. BUSMASTERING - when peripherals in a computer can transfer data directly into the system's main memory (RAM) via the main bus in the PC without having to wait for the CPU to do it for them. DMA interfaces are such and example.

DACs:

Digital to Analog Converter. A device that converts digital signal to analog, such as for speakers (in sound cards) and monitors (RAMDAC in video cards). The opposite happens in analog to digital converters.

TRANSDUCER:

A mechanism that translates energy signals

FLAGS AND INTERRUPTS:

Flag: is a bit of information that is either in one of 2 states: on or off. The state of the flag determines instructions.

Polling: Is simply to check teh status of and input line, sensor or memory location to see if a particular external event has been registered. It involves a node inspecting the communication hardware - typically a flag bit - to see if natural synchronization of the nodes imposed by polling is used in the implementation of communicating process cannot perform any other operations until the communication has completed.

HANDSHAKING:

Predetermined hardware or software activity designed to establish or maintain 2 machines in programs in sync. Handshaking often concerns the exchange of messages or packets of data between 2 systems with limited buffers. Hardware handshaking uses voltage levels or pulses on wires to carry the handshaking signals whereas the method used by 2 modems to establish contact with each other and to agree on baud rate, error correction and compression protocals.

MOTHERBOARDS:

The main printed circuit board in an electronic device, particularly a computer, which contains sockets that accept additional boards. The bus is the main circuit on the motherboard that serves to link and transfer data between the devices and peripherals connected to the motherboard.

PERIPHERAL DEVICES:

Any part of a computer other than the CPU or working memory

DEVICE DRIVERS:

Software to control a hardware component

CHECK SUMS:

A sum generated using individual digits of a number and employed as an error-detecting device.