CS 2734 Computer Organization II

Read pages 111-120 (Sections 3.4.1 - 3.4.4) of Tanenbaum

• Floating point conversions
  By popular request, we'll go over the following floating point conversions:
  • $0.5\; =\; 1.0\; x\; 2-1$ has a representation 3F000000H.
  • $1\; =\; 1.0\; x\; 20$ has a representation 3F800000H.
  • $1.5\; =\; 1.1\; x\; 20$ has a representation 3FC00000H.

• Categories of control lines:
  • Bus control
  • Interrupts
  • Bus arbitration
  • Coprocessor signaling
  • Status
  • Other

• Some terminology:
  • Pinout refers to the meaning of signals on various pins of a chip (address, data, control).
  • Asserted means to cause an action. (For example A is asserted high, but NOT A is asserted low.)
  • Negated is the opposite of asserted.
  • A bus is an electrical pathway between multiple devices.
  • The rules for accessing the bus are called the bus protocol.
  • A bus master is an active device that can initiate a bus transfer.
  • A slave is a passive device that can only wait for requests.

• Synchronous bus:
  • Driven by a crystal.
  • Cycles of fixed length.
  • The original PC bus and its extensions are examples of synchronous bus technology.
  Control on a synchronous bus is a little simpler, but the fixed cycle limits the use of new faster technology.

• Asynchronous bus:
  • Control done by master slave handshake with MSYN and SSYN line.
  • More flexible.
  • The VME bus is an example of asynchronous bus technology.

Revision Date: 4/21/97 at 7 p.m.