The need to make your own components

  • Components - like the multiplexor can be designed to peform a useful function

  • Often, we will need multiple copies of a component to contruct a circuit

  • EDiSim provide this way to use multiple copies of a component easily:

      1. You define the component once (in the definition, you specify how the component is built (connected)
      2. You can then instantiate any number of the copies of the component

A concrete example

We have learned how to make a multiplexor circuit previously:

We must to make many connections to construct a multiplexor circuit !!!

A concrete example

Suppose we need more multiplexor circuits in our project:

How can we avoid make all the (similar) connections all over again ?

Define and instatiating sser-defined circuit components
 

Syntax to define a user-defined circuit component: 

 Define  CompName  inSigParams  | outSigParams ;  
    CircuitComponent1;
    CircuitComponent2;
    ....
    ....
 Endef;

Syntax to use a (already defined) user-defined circuit component: 

 CompName  coord  inputSigs  | outputSigs ;

Example: defining the multiplexor as a user-defined circuit component
 

We have previously studied the multiplexor circuit:

The input signals are: i3, i2, i1, i0 and c1, c0
The output signal is: z

Example: defining the multiplexor as a user-defined circuit component
 

(1): specify the component name, input signal names and the output signal name(s): 

Define MyMux i3 i2 i1 i0 c1 c0 | z; 
 
 


 
 
  

 
Endef;

The input signals are: i3, i2, i1, i0 and c1, c0
The output signal is: z

Example: defining the multiplexor as a user-defined circuit component
 

(2): use the input names as inputs signals to compute the output signal(s): 

Define MyMux i3 i2 i1 i0 c1 c0 | z; 
  Not aa   c1 n_c1;
  Not aa   c0 n_c0;

 
 

  

 
Endef;

(2a): connect the NOT-gates
 

Example: defining the multiplexor as a user-defined circuit component
 

(2): use the input names as inputs signals to compute the output signal(s): 

Define MyMux i3 i2 i1 i0 c1 c0 | z; 
  Not aa   c1 n_c1;
  Not aa   c0 n_c0;

  And aa   i0 n_c1 n_c0    o_0;
 

  

 
Endef;

(2b): connect the first AND-gates
 

Example: defining the multiplexor as a user-defined circuit component
 

(2): use the input names as inputs signals to compute the output signal(s): 

Define MyMux i3 i2 i1 i0 c1 c0 | z; 
  Not aa   c1 n_c1;
  Not aa   c0 n_c0;

  And aa   i0 n_c1 n_c0    o_0;
  And aa   i1 n_c1   c0    o_1;
  And aa   i2   c1 n_c0    o_2;
  And aa   i3   c1   c0    o_3;

 
Endef;

(2c): connect the other AND-gates
 

Example: defining the multiplexor as a user-defined circuit component
 

(2): use the input names as inputs signals to compute the output signal(s): 

Define MyMux i3 i2 i1 i0 c1 c0 | z; 
  Not aa   c1 n_c1;
  Not aa   c0 n_c0;

  And aa   i0 n_c1 n_c0    o_0;
  And aa   i1 n_c1   c0    o_1;
  And aa   i2   c1 n_c0    o_2;
  And aa   i3   c1   c0    o_3;

  Or  aa   o_3  o_2  o_1 o_0   z ;
Endef;

(2d): connect the OR-gates and compute the output signal z !
          DONE !!!

Example: use a user-defined circuit component
 

Example: we can instantiate/create two MyMux components as follows: 

  MyMux  aa  x3 x2 x1 x0 c1 c0 | o1;   // Mux 1

  MyMux  aa  y3 y2 y1 y0 c1 c0 | o2;   // Mux 2

Mux1 will multiplex the inputs x3 x2 x1 x0 to the output o1
Mux2 will multiplex the inputs y3 y2 y1 y0 to the output o2

Both multiplexors are controlled by the control signal c1 c0

Example: use a user-defined circuit component

Example EDiSim circuit program with a MyMux component: 

Define MyMux i3 i2 i1 i0 c1 c0 | z;
  Not    fb   c1 n_c1;
  Not    fb   c0 n_c0;

  And    dc   i0 n_c1 n_c0    o_0;
  And    ec   i1 n_c1     c0    o_1;
  And    bc   i2     c1 n_c0    o_2;
  And    ac   i3     c1     c0    o_3;
  Or     cd   o_3  o_2  o_1 o_0   z;
Endef;

Switch aa sw3 '3' ZERO;
Switch ba sw2 '2' ZERO;
Switch ca sw1 '1' ZERO;
Switch da sw0 '0' ZERO;

Switch gb sw4 '4' ZERO;
Switch gc sw5 '5' ZERO;

MyMux ab-ec sw3 sw2 sw1 sw0 sw5 sw4 | out;

Probe ce  out;

DEMO: /home/cs355001/demo/circuits/mux.m

Type control-M to "zoom in" and control-N to "zoom out"

Important mistake to avoid when defining a user-defined component

Important note:

  • Very important:

    • Input and output signal names in a user-defined circuit component must be unique !!!

  • Do not use the same signal name in the input/output signal list in a circuit definition

    Examples: 

    Define MyMux i0 i2 i1 i0 c1 c0 | z;
  ....

Define MyMux i0 i2 i1 z c1 c0 | z;
  ....

  • This practice will cause serious compile erros in EDiSim

Why do we need multiple multiplexors ?
 

One 4×1 multiplexor allows us to select one 1 bit number among 4 1 bit numbers:

 
 

(In general, a 2n×1 multiplexor allows us to choose one 1 bit number among 2n 1 bit numbers)

Why do we need multiple multiplexors ?
 

Suppose we want to select one 2 bits number among 4 2 bits numbers

 
 

Outputs z1 z0 is equal to one of the inputs d1 d0, c1 c0, b1 b0 or a1 a0 depending on the values c1 c0

Why do we need multiple multiplexors ?
 

Solution: we use one 4×1 multiplexor to select the bit 0 of each number:

 
 

Outputs z0 is equal to one of the inputs d0, c0, b0 or a0 depending on the values c1 c0

Why do we need multiple multiplexors ?
 

Solution: we use another 4×1 multiplexor to select the bit 1 of each number:

 
 

Outputs z1 is equal to one of the inputs d1, c1, b1 or a1 depending on the same values c1 c0

I.e.: the 2 multiplexors work in parallel, each one selecting one bit of the same 2 bits (binary) number !!

DEMO:: /home/cs355001/demo/circuits/parallel-mux