Safe Phased Logic Counter : Phased Logic Example

A description of the schematic is given below. It contains all the components that are described in the live phased logic design. In order to make it safe, certain elements were added to the design.

• The additional components of the schematic are :
  
  • C1 and C4 are 3 input C-elements.
  • C2, C3 and C5 are 2 input C-element gates.
    The C-element or completion element asserts a high output when all of its inputs are high and asserts a low output when all of its inputs are low.

Observations...

• In order to limit the number of tokens to one on any given loop, feedback loops are added to each of the nets in the design. The circuit is now SAFE due to the addition of feedback loops. The feedback loops can be added only if the following rules are satisified :
  
  • The starting point of the loop is a buffer or a barrier gate and its destination is a normal gate.
  • The starting point is a normal gate but its destination is a barrier gate.
  • The starting and ending points are normal gates with the addition of a token in the loop.

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