CHAPTER 6: INPUT/OUTPUT

CHAPTER 6: INPUT/OUTPUT

1. External Devices

   • Human Readable
   • Machine Readable
   • Communication

2. Keyboard/Monitor

   • Computer & User interaction
   • User provides input through the keyboard
   • Monitor display data provided by computer

3. Function of I/O Module

   • Control & Timing
   • Processor communication
   • Device communication
   • Data buffering
   • Error detection

4. Programmed I/O

   • Data exchange between processor & I/O Module
   • Processor executes program direct control of I/O operation
   • if the processor is busy, it must wait until I/O operation is complete
   • if the speed of processor is faster than I/O module, this is wasting processor time

5. I/O Commands

   • write
   • control
   • test
   • read

6. I/O Mapping

   • memory mapped I/O, device and memory share an address space
   • isolated I/O separate address space

7. Interrupt-Driven I/O

   • processor has to wait I/O module to be ready
   • issue an I/O command to module, and go do something else
   • I/O module will interrupt processor when device is ready
   • processor execute data transfer then continue other jobs

8. Device Identification

   • software poll
   • daisy chain
   • bus arbitration
   • multiple interrupt lines

9. USB

   • commonly use high speed I/O
   • controlled by root host attaches device to create local network with hierarchical tree topology
   • widely used for extra connection
   • default for slower speed devices