Распиновка Термины и определения

• Задать вопрос
• Comment
• Редактировать
• добавить новую

Interfaces
When looking at interfaces the are a lot of misconceptions. Some times people call a connector an interface, while in a real interface is more then that. A complete interface consists of three parts:
Connector
Pin assignment
Electrical characteristics

Connector
The connector is defined by it shape, it"s size and the amount of pins it holds and of course the place the pins are mounted in the connector housing. Mostly it is built up of a shell (which contains the pins), the pins, the hood and something to mount it with like screw-locks or latches. Pin assignment
The pin assignment describes which pin is connected to which circuit and thus describes the actual function. Electrical characteristics
The electrical characteristics describe the voltages, currents and shapes of the signals.

DTE and DCE

The terms DTE and DCE are very common in the datacommunications market. DTE is short for Data Terminal Equipment and DCE stands for Data Communications Equipment. But what do they really mean? As the full DTE name indicates this is a piece of device that ends a communication line, whereas the DCE provides a path for communication.

Let"s say we have a computer on which wants to communicate with the Internet through a modem and a dial-up connection. To get to the Internet you tell your modem to dial the number of your provider. After your modems has dialed the number, the modem of the provider will answer your call and your will hear a lot of noise. Then it becomes quiet and you see your login prompt or your dialing program tells you the connection is established.
Now you have a connection with the server from your provider and you can wander the Internet.

In this example you PC is a Data Terminal (DTE). The two modems (yours and that one of your provider) are DCEs, they make the communication between you and your provider possible. But now we have to look at the server of your provider. Is that a DTE or DCE?
The answer is a DTE. It ends the communication line between you and the server. Although it gives you the possibility to surf around the glode. The reason why it is a DTE is that when you want to go from your provides server to another place it uses another interface. So DTE and DCE are interface dependend. It is e.g. possible that for your connection to the server, the server is a DTE, but that that same server is a DCE for the equipment that it is attached to on the rest of the Net.

Unbalanced
An unbalanced signal has a ground signal which is the common for all other signals and the actual signal voltage is measured in reference to this ground signal.
So if there is stated that the voltage for a signal is +12 Vdc for a one and -12 Vdc for a zero, that means that those voltages are measured in reference to the ground signal.

NOTE: Normaly the ground signal is said to be 0 Vdc, but it is possible that the line carries a voltage e.g. 220 Vac. What happens is that the signal voltages will then be superimposed on the 220 Vac, so the actual measured voltage at the receiver side is still only the signal voltage.

Balanced
A balanced signal has no ground reference. The measured voltage is defined as the voltage difference between two copper lines, normaly refered to as line A and B. So for every signal that needs to be transfered you will have two leads.
The signals can be defined in two ways:

• The voltage difference between A and B can be an one when e.g. 12 volt and a zero when e.g. 6 volt.
• The voltage difference between A and B can be an one when A>B or a zero when B>A.

Some terms and abbriviations

AC:

Access Control

ACE:

Automatic Calling Equipment

ACK:

ACKnowledge

ACR:

Abandon Call and Retry

ADSP:

Appletalk Data Stream Protocol

AEP:

Appletalk Echo Protocol

AFP:

Appletalk Filing Protocol

ARCnet:

Attached Resource Computer NETwork

ASP:

Appletalk Session Protocol

ATP:

Appletalk Transport Protocol

BN:

Bridge Number

BSA:

Basic Service Area

BSS:

Basic Service Set

CDDI:

Copper Distributed Data Interface

CMSA/CA:

Carrier Sense Multiple Access with Collision Avoidance

CP:

Continuation Pointer

CRC:

Cyclic Redundancy Check

CRQ:

Call Request

CSMA/CA:

Carrier Sense Multiple Access with Collision Avoidance

CSMA/CD:

Carrier Sense Multiple Access with Collision Detect

CTS:

Clear To Send

CUG:

Closed User Group

D:

Direction bit

DA:

Destination Address (MAC)

DAS:

Dual Attached Station

DCD:

Data Carrier Detect, officially known as Received Line Signal Detector

DCE:

Data Communications Equipment

DCLA:

DC Level Adjust

DDP:

Datagram Delivery Protocol

DID:

Destination IDentifier

DIX:

Digital Intel Xerox

DLO:

Data Line Occupied

DPR:

Digit Present

DR:

Date Rate

DSAP:

Destination Service Access Point

DSC:

Distant Station Connected

DSR:

Data Set Ready, officially known as DCE Ready

DSSS:

Direct Sequence Spread Spectrum

DTE:

Data Terminal Equipment

DTR:

Data Terminal Ready, officialy known as DTE Ready

ED:

Ending Delimiter

ELAP:

Ethernet Link-Access Protocol

ENQ:

Enquiry

EOT:

End Of Transmission

ESA:

Extended Service Area

ESS:

Extended Service Set

FBE:

Free Buffer Enquiry

FC:

Frame Control

FCS:

Frame Check Sequence

FDDI:

Fiber Distributed Data Interface

FHSS:

Frequency Hopping Spread Spectrum

FS:

Frame Status

GFI:

General Format Identifier

HDLC:

High level Data Link Control

IGRIP:

Interior Gatway Routing Information Protocol

IR:

Infrared

IRL:

Inter Repeater Link

IS:

Internet System

ISO:

International Standards Organisation

ISU:

Information Symbol Unit

ITT:

Invitation To Transmit

LAN:

Local Area Network

LAPB:

Link Access Procedure Balanced

LCN:

Logical Channel Number

LF:

Largest Framesize

LGN:

Logical Group Number

LLAP:

Localtalk Link-Access Protocol

LLC:

Logical Link Control

LTH:

Length

MAC:

Media Access Control

MDI:

Medium Dependent Interface

MII:

Medium Independent Interface

MPDU:

MAC Protocol Data Unit

Modem:

MOdulator DEModulator. A device for connecting two DTEs.

NAK:

Negative AcKnowledge

NBP:

Name-Binding Protocol

NIC:

Network Interface Card

NID:

Next IDentification

OSI:

Open Systems Interconnect

OSPF:

Open Shortest Path First

PAC:

Packet

PAD:

Packet Assembler/Disassembler

PAP:

Printer Access Protocol

PCM:

Pulse Code Modulation

PHY:

Physical

PLCP:

Physical Layer Convergence Protocol

PLP:

Packet Layer Protocol

PMD:

Physical Medium Dependent

PMI:

Physical Medium independent sublayer

PND:

Present Next Digit

PPP:

Point-to-Point Protocol

PSDU:

Physical Sublayer Data Unit

PTI:

Packet Type Identifier

PVC:

Permanent Virtual Circuit

RC:

Routing Control (16 bits)

RD, RxD:

Received Data

RDx:

Route Designator x

RI:

Routing Information

RII:

Routing Information Indicator

RIM:

Resource Interface Module

RIP:

Routing Information Protocol

RSU:

Reconfiguration Symbol Unit

RT:

Routing Type

RTMP:

Routing Table Maintenance Protocol

RTS:

Request To Send

SA:

Source Address incl. RII

SABM:

Set Asynchronous Balanced Mode

SABME:

SABM Extended

SAS:

Single Attached Station

SC:

System Code

SD:

Starting Delimiter

SDH:

Synchronous Digital Hierarchy

SFD:

Start Frame Delimiter

SGND:

Signal GrouND

SID:

Source IDentification

SN:

Segment Number

SNAP:

SubNetwork Addressing Protocol

SOH:

Start Of Header

SONET:

Synchronous Optical NETwork

SSAP:

Source Service Access Point

STP:

Shielded Twisted Pair

SVC:

Switched Virtual Circuit

TD, TxD:

Transmitted Data

THT:

Token Holding Time

TLAP:

Token ring Link-Access Protocol

TP-PMD:

Twisted Pair PMD

TRT:

Token Rotation Time

TTRT:

Target Token Rotation Time

UTP:

Unshielded Twisted Pair

WAN:

Wide Area Network

ZIP:

Zone Information Protocol