Paper About OS && Hardware

保护模式下

8259A芯片编程及中断处理探究

http://blog.csdn.net/xiaohan13916830/archive/2004/06/26/27009.aspx

http://blog.csdn.net/xiaohan13916830/archive/2004/06/27/27642.aspx

Linux中断解析

http://blog.csdn.net/kanghua/archive/2007/10/25/1843788.aspx

微型计算机技术 http://202.114.200.211:7310/netclass/weixingjisuanji/

电脑怎样让我们看到图像和听到声音的呢？其实这个问题就是电视的显示原理。
图像实际上是由脉冲电流（即所谓数字信号）信号通过一段电线传给CRT的内部电路，再经电子枪发射电子束轰击荧光磷粉产生图像。即通过电子轰击荧光粉使电信号变成了光信号。
声音则是该电流流过电磁线圈时，会产生某频率的电磁场（与声波频率相似），这个电磁场与永久磁体的磁场相互作用，就推动了纸盆振动。于是声音就从喇叭中发出来了。即电流使纸盆（空气）发生某种频率的振动而发出声音，实现了电信号转变为声信号。

更形象地说明：按下键盘，主机集成电路中某些位置的电路中的电流（强度）发生了变化，该电流的变化经过了复杂的集成电路系统后逐步得到一个脉冲电 流信号，此电流又传递到CRT的电路系统，CRT又将电流的变化转变成显像管中电子轰击荧光屏的位置变化产生了图像。同时，另一部分脉冲电流经过了一个电 磁线圈时产生磁场，推动另一个与磁体相连的纸盆振动发出了声音。

结论:
我们按键盘输入各种程序，目的只是为了在大规模集成电路的许多不同的位置产生多种电流的输入，这些电流经过了电脑主机里面集成电路系统的处理后，得到了一个脉冲电流，传递到CRT的电路系统，于是电子束达到了各种所需的偏转的角度，正确的打在了荧光屏上产生了图像。
如此看来，我们输入那么多字母，最终只是为了改变显像管中电子偏移的角度，使它打到正确的位置产生正确的图像。另外的成果就是产生某种电流最终使 喇叭中的纸盆振动发出了声音。这种通过敲键盘(所谓编程)改变电流来制作图像和声音的过程，我们为此起了个很玄的名字——生活数字化。


Key Board---How it Works

How it works

The following briefly describes a "dome-switch" keyboard (sometimes incorrectly referred to as a membrane keyboard), the most common type in use today:

1. When a key is pressed, it pushes down on a rubber dome sitting beneath the key. A conductive contact on the underside of the dome touches (and hence connects) a pair of conductive lines on the circuit below.
2. This bridges the gap between them and allows electric current to flow (the open circuit is closed).
3. A scanning signal is emitted by the chip along the pairs of lines to all the keys. When the signal in one pair becomes different, the chip generates a "make code" corresponding to the key connected to that pair of lines.
4. The code generated is sent to the computer either via a keyboard cable (using on-off electrical pulses to represent bits) or over a wireless connection. It may be repeated.
5. A chip inside the computer receives the signal bits and decodes them into the appropriate keypress. The computer then decides what to do on the basis of the key pressed (e.g. display a character on the screen, or perform some action).
6. When the key is released, a break code (different than the make code) is sent to indicate the key is no longer pressed. If the break code is missed (e.g. due to a keyboard switch) it is possible for the keyboard controller to believe the key is pressed down when it is not, which is why pressing then releasing the key again will release the key (since another break code is sent).