CS 2734 Computer Organization II

Read Tanenbaum p. 161-170 (Section 4.1). Please bring your book to class for the next few weeks

The goal of this part of the course is to understand what control is needed to execute the instruction cycle in a simple machine (specifically the machine in Tanenbaum 4-16). This is not a course in logic design. You will need to know enough notation to be able to read and understand simple circuit diagrams.

• Symbols for 5 basic gates (NOT, NAND, NOR, AND, OR).
  (See Tanenbaum Figure 3.2 for symbols and truth table.)

• Boolean expressions: overbar (NOT), + (OR) and . (AND)

• Combination circuit - one in which the outputs are uniquely determined by the current inputs. Circuits which have memories are not combinational.

• The key components needed to understand instruction cycle control:
  • multiplexer:
    (2ⁿ inputs, n control lines and one output): an n-bit address selects one of 2ⁿ data lines. (Look carefully at Tanenbaum Figures 3-12 and 3-13.)

  • decoder:
    (n bit input selects one of 2ⁿ outputs). (Look carefully at Tanenbaum Figure 3-14.)

  • clock:
    circuit that emits pulses of a precise width and interval. (Look carefully at Tanembaum Figure 3-22.)

  • registers and latches:
    provide memory.

  • buses:
    for now just think of buses as connections allowing information to flow between two points. (We'll look at details later.)

Revision Date: 3/5/97