INPUT/OUTPUT

1. INTRO

1.1. a device which is connected to an I/O modules of computer

1.2. third key element of a computer system

2. ISSUES

2.1. data transfer rate or peripheral is slower than the memory or processor

2.2. peripheral use different data formats

3. TYPE OF EXTERNAL DEVICES

3.1. Human Readable

3.1.1. suitable for communicating with computer user

3.2. Machine Readable

3.2.1. suitable for communicating with equipment

3.3. Communication

3.3.1. suitable for communicating with remote devices

4. INTERFACE TO EXTERNAL

4.1. Control Signal

4.2. Data Signal

4.3. Status Signal

5. KEYBOARD/MONITOR

5.1. common means of computer or user interaction

6. MAJOR FUNCTIONS I/O MODULES

6.1. Control & Timing

6.2. Processor Communication

6.3. Device Communication

6.4. Data Buffering

6.5. Error Detection

7. INTERRUPT DRIVEN I/O

7.1. Overcomes CPU waiting

7.2. No repeated CPU checking of device

7.3. I/O module interrupts when ready

8. DIRECT MEMORY ACCESS (DMA)

8.1. allows certain hardware subsystems to access main memory (RAM) of CPU

8.2. a way for I/O devices to bypass the CPU when accessing memory

8.3. DMA is the answer for limited transfer rate and CPU tied up