6.5.4 Explain how peripheral devices are controlled with reference to the printer, modem, and disk drive.
Teaching Notes:
This must include the use of buffers (including double buffering), interrupts and interrupt priorities, polling, direct memory access (DMA) and handshaking in these devices.
Sample Question1:
5. Outline what is meant by double buffering. [2 marks]
Sample Question 2:
A small company has a LAN connecting its various desk-top computers and
peripheral devices.
(a) Explain, with an example, how handshaking might be used during data
transmission over this LAN. [2 marks]
JSR Notes:
****Note that it makes more sense to go through 6.5.5 before looking at the specific application of these points in 6.5.4.
But until I re-write this, you have got everything you should need right on page 349 and 350. It’s just that you do have to be able to make sense of this and be able to recall it. It actually would be a good idea for you to go through each one of these set pieces, and put them in your own words – making sure that you include all the 6.5 terms that apply.
Still, there is one thing mentioned in the teaching notes that is not covered well back in the 6.5.2 section: double-buffering. See the explanation previous of buffer. But the idea here is that you can make your buffering system more efficient if while you are emptying one buffer, you are filling up another (the assumption is that you can’t do both at the same time to the same buffer.) An analogy that works well here is that you want to fill up the inflatable swimming pool in the back yard, and have only one bucket, versus two. If you have two, while you are emptying the one, you leave the other to fill up, and then you switch, and so on and so on.