Hardware

• microcomputers as lab instruments
  

• inside an IBM PC

  Figure 6.1: Essential elements of a personal computer

  
  • the mother board: CPU, RAM, BIOS, some I/O & timing circuits
  • the I/O bus: expansion cards

    Note: CPU often has a separate, faster & wider bus to access memory (RAM)

  • I/O card and the connection to the outside world
  • operation of the computer boils down to controlled transfer and manipulation of bits (digital on/off, 0V/5V levels) among various components
  • complex operations: many clock cycles; some devices may have to wait; computer is not a ``real-time'' device! -- but latency is small
  • structure of a computer bus: address lines -- which device is getting/sending data; auxiliary -- the timing of the transfer, handshaking; data lines AD0-AD7 -- the data may be a real number, a machine instruction, a part of an address, etc.
• A typical I/O interface:
  • I/O card inside a PC
  • ribbon cables
  • distribution module at the workstation
  • optoisolators and separate commons
  • 4 x 8-bit input & 4 x 8-bit output parts
  • multiplexed 4-input, 12-bit A/D converter (bipolar $\pm$ 10V)
  • 2 x 12-bit D/A outputs (bipolar $\pm$ 10V)
  • counter & timer circuits