Sim-Ex™ Tutorial for A+ : Hardware

Cables and Connectors

Serial Ports:

The serial port is an Asynchronous port which transmits data one bit of data at a time. Serial port hardware usually consists of a UART (Universal Asynchronous Receiver/Transmitter).

Most commonly used serial ports are given below:

1. DB9:

DB9 adheres to the RS-232c interface standard. It has 9 pins as shown in the figure. The connector is "D" shaped, and easy to recognize. The function of each pin is described below.

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Outline Diagram of DB-9

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DB-9 Female Connector

Pin Description:

Pin # Pin Description
Pin 1 Data Carrier Detect DCD
Pin 2 Received Data RxData
Pin 3 Transmitted Data TxData
Pin 4 Data Terminal Ready DTR
Pin 5 Signal Ground Gnd
Pin 6 Data Set Ready DSR
Pin 7 Request To Send RTS
Pin 8 Clear To Send CTS
Pin 9 Ring Indicator RI

2. DB25:

DB25 adheres to the RS-232C interface standard. It has 25 pins as shown in the figure. The connector is "D" shaped, and easy to recognize. DB-25 is normally used in older computers, and not much used in modern day computers.

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3. RJ-11:

RJ-11 is a 4-wire connector, commonly used with a modem. It should not be confused with bigger RJ-45 cable and connector. RJ-45 is commonly used for Ethernet network interface card (NIC).

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Schematic of RJ-11 Connector

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An RJ-11 Cable with Connector

Pin # Function
A1 Ground
A2 Rx (Data Input)
A3 Tx (Data Output)
A4 Vc (Power)

4. RJ-45:

An RJ-45 connector has 4 pairs of wires as shown in the schematic diagram below. Note that an RJ-11 is a 4-wire connector, where as RJ-45 is an 8-wire connector.

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RJ-45 connector schematic

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RJ-45 connector crimped to a cable.

RJ-45 connector is commonly used for Ethernet Networking ports. Devices that normally use RJ-45 ports include NICs, Hubs, Switches, and Routers.

There are basically two types of cables. One is Straight-through cable, and the other is Cross-over cable. Straight-through cables are used for connecting a network device to a work station. Cross-over cables are used for connecting a hub to a switch or a hub to another hub.

Parallel Ports:

1. DB-25

DB-25 connector is most commonly used in conjunction with a parallel printer. It has an 8 bit data bus as shown in the figure below.

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Pin # Function
Pin 1 Strobe
Pin 2 Data Bit 0
Pin 3 Data Bit 1
Pin 4 Data Bit 2
Pin 5 Data Bit 3
Pin 6 Data Bit 4
Pin 7 Data Bit 5
Pin 8 Data Bit 6
Pin 9 Data Bit 7
Pin 10 Acknowledge
Pin 11 Busy
Pin 12 Paper End
Pin 13 Select
Pin 14 Auto Feed
Pin 15 Error
Pin 16 Initialize Printer
Pin 17 Select Input
Pin 18 - Pin 25 Ground (return for pins 0-7)

The length of Parallel Printer cable usually limited to a maximum of 15 feet

Other Type of Parallel Ports:

Enhanced Parallel Port (EPP): The Enhanced Parallel Port (EPP) operates close to ISA bus speed and can achieve transfer rates up to 1 to 2MB/sec of data.

Enhanced Capabilities Port (ECP): The Enhanced Capabilities Port (ECP), is an additional enhanced Parallel port.

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