Explain how peripheral devices are controlled with reference to the printer, modem and disk drive.

Printing a document
  1. User clicks 'print'
  2. Computer polls the printer to determine when it is ready
  3. Once it is ready, the printer & computer perform a handshake
    • The handshake ensures that the connection is established & that the printer and computer are actually able to communicate (if correct drivers are installed on the computer, for ex.)
    • If there is some kind of problem (ex. the toner is low) an interrupt is sent to the CPU
  4. Document to print is stored in a buffer and sent to the printer, where it might be stored in another buffer before it is finally printed
  5. Once the printer is finished & ready to perform the next printing task, it indicates this to the computer

Modem to modem communication
  1. A handshake is performed to initiate the connection
    • The handshake checks whether both modems use the same protocols. Usually the modems will check if the other device supports the fastest protocols first and then work backwards until a protocol is found, which is supported by both devices.
  2. If a protocol is found, which is supported by both devices, the modem indicates to the computer that it is ready to be used. If the modem can't establish a connection, it will send an interrupt to the computer that the channel is not available.

Disk drive
Controlled with the disk drive controller:
  1. Computer indicates to the controller, that it wants to read data from or write data to the disk
  2. Data is transferred to the buffer of the controller, which then coordinates the rest of the read or write process

Created By: Jocbe
Last update: 17. January 2011