Tuesday, June 30, 2009

Net Work Cards

What is a network card?

A network card (also called a Network Adapter or Network Interface Card, or NIC for short) acts as the interface between a computer and a network cable. The purpose of the network card is to prepare, send, and control data on the network.

A network card usually has two indicator lights (LED's):


* The green LED shows that the card is receiving electricity;

* The orange (10 Mb/s) or red (100 Mb/s) LED indicates network activity (sending or receiving data).

To prepare data to be sent the network card uses a transceiver, which transforms parallel data into serial data. Each cart has a unique address, called a MAC address, assigned by the card's manufacturer, which lets it be uniquely identified among all the network cards in the world.

Network cards have settings which can be configured. Among them are hardware interrupts (IRQ), the I/O address and the memory address (DMA).

To ensure that the computer and network are compatible, the card must be suitable for the computer's data bus architecture, and have the appropriate type of socket for the cable. Each card is designed to work with a certain kind of cable. Some cards include multiple interface connectors (which can be configured using jumpers, DIP switches, or software). The most commonly used are RJ-45 connectors.
Note: Certain proprietary network topologies which use twisted pair cables employ RJ-11 connectors. These topologies are sometimes called "pre-10BaseT ".

Finally, to ensure that the computer and network are compatible, the card must by compatible with the computer's internal structure (data bus architecture) and have a connector suitable for the kind of cabling used.

Friday, June 19, 2009

Video Feature Connector Pinouts.

Pinout details

Pin

Name

Function

1

PD0

Dac Pixel data bit 0

2

PD1

bit 1

3

PD2

bit 2

4

PD3

bit 3

5

PD4

bit 4

6

PD5

bit 5

7

PD6

bit 6

8

PD7

bit 7

9

-

Dac Clock

10

-

Dac Blanking

11

-

Horizontal Sync

12

-

Vertical Sync

13

-

Ground

14

-

Ground

15

-

Ground

16

-

Ground

17

-

Select Internal Video

18

-

Select Internal Sync

19

-

Select Internal Dot Clock

20

-

Not Used

21

-

Ground

22

-

Ground

23

-

Ground

24

-

Ground

25

-

Not Used

26

-

Not Used



And I assume that pins 1 - 12 are outputs, and 17 - 19 are inputs. Is this correct?

The reason is this - I have a Rombo Media Pro+ video digitising card. It chroma keys its output into the vga monitor signal. However, although it is supposed to work with an ET-4000 with Hi-colour RAMDAC, the colours on screen behave as if the top 2 bits of colour information are missing, and red, green, blue signals are swapped around. Rombo has suggested that this may be due to insufficient buffering on the feature connector outputs, and is happy to sell me a buffer device for 50 pounds. I would rather save about 45 pounds, and build my own. I assume it would require (for example) a 74F244 buffer IC(or two).