PyCircPL - Python Logic Circuit Programming Language

• Link to GITHUB repository

• Link to the the Google Colaboratory notebook

  • The Google Colaboratory notebook has the advantage that you can run PyCircPL code from it without having to install PyCircPl or even Python on your local system.
  • You first need to copy it to your google drive (or github repository)
  • You can also dowload it to your local device and open it as a Jupyter notebook (if you have it installed with your Python).

Installing the PyCircPL package

• The PyCircPL package can be installed on your local system by running the following command from the command line

  pip install pycircpl

• Or you may try running one of the following commands from this notebook.
• If you are running it from a Jupyter notebook on your local system, then it will be installed on your device.

# To install from this notebook, run this cell.
%pip install pycircpl
# This should also work:
# !pip install --upgrade pycircpl

# After installation, you have to restart this notebook.
# Make sure to comment the %pip or !pip lines above to avoid reinstall each time you run this notebook.

# To uninstall the package use:
#%pip uninstall pycircpl
# or
# !pip uninstall pycircpl

Looking in indexes: https://pypi.org/simple, https://us-python.pkg.dev/colab-wheels/public/simple/
Collecting pycircpl
  Downloading pycircpl-1.1.tar.gz (2.2 kB)
Building wheels for collected packages: pycircpl
  Building wheel for pycircpl (setup.py) ... done
  Created wheel for pycircpl: filename=pycircpl-1.1-py3-none-any.whl size=1914 sha256=2b17b91d8b346628045b2fdb55ff13f846d76e9767c72369dca41d035feea87f
  Stored in directory: /root/.cache/pip/wheels/a3/2d/3b/c702335f765a1d7dfba13c8b049fbcc51bb63fabfe3a5c1938
Successfully built pycircpl
Installing collected packages: pycircpl
Successfully installed pycircpl-1.1

• After installation, you may need to restart this notebook.

Loading the PyCircPL package

• After installing the PyCircPL package, you need to import it.
• The following command imports PyCircPL to your Python interpreter.

from pycircpl import *

Introduction

• PyCircPL is a simple Python package for simulating Logic Circuits specifically designed for educational use in introductory computation and digital logic college courses.
• As such, it was primarily tuned for simplicity, readability, convenience, and fast learning curve.
  • Less for speed or industrial production.
• It is a lightweight package especially designed for small to medium scale circuits, such as those that are studied in introductory academic courses on the theory of computation and electronic digital design.
• Its main characteristic is that a digital circuit or a boolean formula can be easily defined by a series of simple Python commands, rather than an external static language.
• So, the only requirement is basic knowledge of the Python programming language, with a little programming skill.
• Experienced Python programmers can probably benefit a lot more from this package.
• It can be a useful companion for theoretical courses on computation models and languages who wish also to engage the students with some programming experience and skills.
  • It is planned to be used in such a course by the author (Hebrew book at http://samyzaf.com/afl.pdf).
  • It enables students to easily model and experiment with
    • Typical logic circuit design
    • Logic Circuit or Boolean formula Validation
    • Logic Circuit Testing
    • Logic problem solving
• It does provide an opportunity for students to develop and practice some programming skills while covering the theoretical computation course.
• In this tutorial, we will cover:
  1. Basic usage of PyCircPL for simulating Logic Circuits or Boolean formulas.
  2. A short survey of the commands and tools of the PyCircPL package.
  3. Advanced usage of PyCirc for experienced Python programmers (TODO).

Example 1: Simulating the circuit FOO

• We start with a very simple logic circuit which we call "FOO" whose PyCirc Diagram is given below

  • Inputs gates: $x_1$, $x_2$, $x_3$
  • Output gates: $y_1$, $y_2$
  • Logic formula: $(y_1, y_2) = (x_1 \land x_2 , \ \neg x_3)$

  • See https://www.samyzaf.com/pycirc/pycirchdl.html for detailed information on PyCirc diagrams.

    

• Here is the PyCircPL code for modeling this circuit:

def FOO(x1, x2, x3):
    g1 = AND(x1, x2)
    g2 = NOT(x3)
    y1 = g1
    y2 = g2
    return y1, y2

• Notic that this is a pure Python code!

  • So you need to run its cell in order to execute it.

• A circuit definition starts with the stabdard Python keyword def which is used to define a Python function.

• The function name is identical to the circuit name FOO.
• The function argument list is identical to the circuit boolean input list x1, x2, x3.

• The function output list (in the last return statement) is identical to the circuit output list.

• Note that we could make the definition shorter by removing the two intermediate variable g1 and g2, but their presence keeps a resemblance with the circuit diagram.

• We ephasize again: the above definition of FOO is a pure Python function!

• This means that you can use in any othe Python code and in other programs/scripts for building new circuit functions.

• Here is a simple example which computes the circuit for the input

  x1 = 1
  x2 = 1
  x3 = 0
  

y1,y2 = FOO(1,1,0)
print(f"y1={y1}")
print(f"y2={y2}")

y1=1
y2=1

Here is a more sophisticated example for Pyhton programmers for generating the Truth Table of FOO. That is, all possible outputs.

for x1 in [0,1]:
  for x2 in [0,1]:
    for x3 in [0,1]:
      y1,y2 = FOO(x1,x2,x3)
      print(f"FOO({x1},{x2},{x3}) = {y1}, {y2}")

FOO(0,0,0) = 0, 1
FOO(0,0,1) = 0, 0
FOO(0,1,0) = 0, 1
FOO(0,1,1) = 0, 0
FOO(1,0,0) = 0, 1
FOO(1,0,1) = 0, 0
FOO(1,1,0) = 1, 1
FOO(1,1,1) = 1, 0

• After successful design of a circuit function such as FOO, it can be placed in a single python code file and loaded as usual with the Python import command.

• You may want to copy the function library that we use in this notebook to your local pc.
• Here is a link to the Python file that contains all functions that we use in this notebook:
  • Click to download functions.py

Example 2: Simulating the circuit FRED

• Here is an example of cell called FRED which uses an instance of the cell FOO as one of its building blocks.
• Note that this cell is using a gate of type FOO whose function we defined in Example 1 above.

• It is easy to write its corresponding function.
• Note that the function FOO is used in the function FRED.

def FRED(x1, x2):
  g0 = 0
  y1,y2 = FOO(x1,x2,g0)
  return y1,y2

Example 3: The circuit HAM

• The follwing cell HAM contains two gates of type FOO and two gates of type XOR3.
• The XOR3 cell is a typical xor cell with 3 input gates.

• It also contains one gate of type NOT.

  

• Here is a PyCircPL code for modeling this cell.
• Notice lines 2 and 3 of the code that use the function FOO.

# CELL: HAM
# This cell is using the FOO cell which we defined earlier
# "XOR" is a basic function in PyCircPL

def HAM(x1,x2,x3,x4):
  g1_y1, g1_y2 = FOO(x1,x3,x2)
  g2_y1, g2_y2 = FOO(x3,x4,x4)
  g3_y = XOR(g1_y2, g1_y1, g2_y2)
  g4_y = NOT(g1_y2)
  g5_y = XOR(g1_y2, g2_y1, g2_y2)
  y1 = g3_y
  y2 = g4_y
  y3 = g5_y
  return y1, y2, y3

• Here is a simple code for generating the truth table of HAM.
• We use the product utility from the itertools module (which is automatically loaded by pycircpl) to generate all the possible combinations of 4 boolean values.

for x1,x2,x3,x4 in product([0,1], repeat=4):
  y1,y2,y3 = HAM(x1,x2,x3,x4)
  print(f"HAM({x1}, {x2}, {x3}, {x4}) = {y1}, {y2}, {y3}")

HAM(0, 0, 0, 0) = 0, 0, 0
HAM(0, 0, 0, 1) = 1, 0, 1
HAM(0, 0, 1, 0) = 0, 0, 0
HAM(0, 0, 1, 1) = 1, 0, 0
HAM(0, 1, 0, 0) = 1, 1, 1
HAM(0, 1, 0, 1) = 0, 1, 0
HAM(0, 1, 1, 0) = 1, 1, 1
HAM(0, 1, 1, 1) = 0, 1, 1
HAM(1, 0, 0, 0) = 0, 0, 0
HAM(1, 0, 0, 1) = 1, 0, 1
HAM(1, 0, 1, 0) = 0, 0, 0
HAM(1, 0, 1, 1) = 0, 0, 0
HAM(1, 1, 0, 0) = 1, 1, 1
HAM(1, 1, 0, 1) = 0, 1, 0
HAM(1, 1, 1, 0) = 0, 1, 1
HAM(1, 1, 1, 1) = 1, 1, 1

Example 4: Simulating 1-bits counter circuit

• The following circuit (given simple digraph represantation) counts the number of 1-bits of its input list.

• This is the correponging Python function:

def COUNT3(x1, x2, x3):
    g1 = AND(x1, x2)
    g3 = XOR(x1, x2)
    g2 = AND(x3, g3)
    g4 = XOR(x3, g3)
    g5 = OR(g1, g2)
    y1 = g5
    y2 = g4
    return y1, y2

• Converting the graph diagram to the corresponding Python code is an easy task.
• Each non-input gate g1, g3, g2, g4, g5, y1, y2, is converted to its corresponding Python statement by simply applying its logical operator on its inputs.
• Note that gate order is critical! You have to go from low to high depth.
• For example, gate variable g3 must be defined befor g2 since it is an input to g2!

• For example, here is what happens we apply COUNT3 on the input list

  x1 = 1 ; x2=0 ; x3 = 1

COUNT3(1,0,1)

(1, 0)

• The number of 1-bits in the input (1,0,1) is 2 which in binary form is (1,0) as the above calculation shows.
• It is easy to verify all possible outcomes of this circuit function with the following code:

for x1,x2,x3 in product([0,1], repeat=3):
  y1,y2 = COUNT3(x1,x2,x3)
  print(f"COUNT3({x1},{x2},{x3}) = ({y1}, {y2})")

COUNT3(0,0,0) = (0, 0)
COUNT3(0,0,1) = (0, 1)
COUNT3(0,1,0) = (0, 1)
COUNT3(0,1,1) = (1, 0)
COUNT3(1,0,0) = (0, 1)
COUNT3(1,0,1) = (1, 0)
COUNT3(1,1,0) = (1, 0)
COUNT3(1,1,1) = (1, 1)

• Note that the same applies if we are given a boolean formula of this logical circuit $$ \begin{array}{rcl} y_1 &=& (x_1 \wedge x_2) \vee ((x_1 \oplus x_2) \wedge x_3) \\ y_2 &=& (x_1 \oplus x_2) \oplus x_3 \end{array} $$ instead of its digraph representation.
• In most cases, the digraph diagram is more intuitive, and easier to work with than the algebraic formula.

Example 5: Simulating a 4x1 Multiplexer

• Multiplxers are important circuit elements in electronic design.

• Here is a simple PyCirc Diagram for a 4x1 Multiplexer circuit (aka MUX2)

  

# Function for MUX2
# input:  x3, x2, x1, x0, s2, s1
# output: y

def MUX2(x0,x1,x2,x3,s1,s2):
    g1_y = NOT(s1)
    g2_y = NOT(s2)
    g3_y = AND(g1_y, x0, g2_y)
    g4_y = AND(g1_y, x1, s2)
    g5_y = AND(s1, x2, g2_y)
    g6_y = AND(s1, x3, s2)
    y = OR(g3_y, g4_y, g5_y, g6_y)
    return y

print("x0  x1  x2  x3 | s1  s2 |  y")
print(30*'-')
for x0,x1,x2,x3,s1,s2 in product([0,1], repeat=6):
    y = MUX2(x0,x1,x2,x3,s1,s2)
    print(f"{x0}   {x1}   {x2}   {x3}  | {s1}   {s2}  |  {y}")

x0  x1  x2  x3 | s1  s2 |  y
------------------------------
0   0   0   0  | 0   0  |  0
0   0   0   0  | 0   1  |  0
0   0   0   0  | 1   0  |  0
0   0   0   0  | 1   1  |  0
0   0   0   1  | 0   0  |  0
0   0   0   1  | 0   1  |  0
0   0   0   1  | 1   0  |  0
0   0   0   1  | 1   1  |  1
0   0   1   0  | 0   0  |  0
0   0   1   0  | 0   1  |  0
0   0   1   0  | 1   0  |  1
0   0   1   0  | 1   1  |  0
0   0   1   1  | 0   0  |  0
0   0   1   1  | 0   1  |  0
0   0   1   1  | 1   0  |  1
0   0   1   1  | 1   1  |  1
0   1   0   0  | 0   0  |  0
0   1   0   0  | 0   1  |  1
0   1   0   0  | 1   0  |  0
0   1   0   0  | 1   1  |  0
0   1   0   1  | 0   0  |  0
0   1   0   1  | 0   1  |  1
0   1   0   1  | 1   0  |  0
0   1   0   1  | 1   1  |  1
0   1   1   0  | 0   0  |  0
0   1   1   0  | 0   1  |  1
0   1   1   0  | 1   0  |  1
0   1   1   0  | 1   1  |  0
0   1   1   1  | 0   0  |  0
0   1   1   1  | 0   1  |  1
0   1   1   1  | 1   0  |  1
0   1   1   1  | 1   1  |  1
1   0   0   0  | 0   0  |  1
1   0   0   0  | 0   1  |  0
1   0   0   0  | 1   0  |  0
1   0   0   0  | 1   1  |  0
1   0   0   1  | 0   0  |  1
1   0   0   1  | 0   1  |  0
1   0   0   1  | 1   0  |  0
1   0   0   1  | 1   1  |  1
1   0   1   0  | 0   0  |  1
1   0   1   0  | 0   1  |  0
1   0   1   0  | 1   0  |  1
1   0   1   0  | 1   1  |  0
1   0   1   1  | 0   0  |  1
1   0   1   1  | 0   1  |  0
1   0   1   1  | 1   0  |  1
1   0   1   1  | 1   1  |  1
1   1   0   0  | 0   0  |  1
1   1   0   0  | 0   1  |  1
1   1   0   0  | 1   0  |  0
1   1   0   0  | 1   1  |  0
1   1   0   1  | 0   0  |  1
1   1   0   1  | 0   1  |  1
1   1   0   1  | 1   0  |  0
1   1   0   1  | 1   1  |  1
1   1   1   0  | 0   0  |  1
1   1   1   0  | 0   1  |  1
1   1   1   0  | 1   0  |  1
1   1   1   0  | 1   1  |  0
1   1   1   1  | 0   0  |  1
1   1   1   1  | 0   1  |  1
1   1   1   1  | 1   0  |  1
1   1   1   1  | 1   1  |  1

Example 6: Simulating a 8x1 Multiplexer circuit

• Now we build a function for a 8x1 Multiplexer circuit (aka MUX3)
• Note that the 8x1 Multiplexer diagram is using our MUX2 circuit as one of its building blocks (two instance of MUX2 are needed).

• We also need one instance of 2x1 Multiplexer (aka MUX1), which we leave to the student as an easy exercise.

  

• As you can see from the diagram we now have 8 inputs bits: x0, x1, x2, x3, x4, x5, x6, x7,
  and one output bit: y.
• We only need 3 logic gates: g1, g2, and g3.
  • g1 and g2 are two instances of MUX2,
  • g3 is an instance of MUX1.
• Here is the code for creating a PyCircPL MUX3 function.
  • We leave to the student to figure out the MUX1 function as an easy exercise.
  • Using the already defined MUX1 and MUX2 functions, it took 5 lines to define the MUX3 function!

def MUX1(x0,x1,s1):
    y1 = NOT(s1)
    y2 = AND(x0, y1)
    y3 = AND(x1, s1)
    y = OR(y2, y3)
    return y

def MUX3(x0,x1,x2,x3,x4,x5,x6,x7,s1,s2,s3):
  g1_y = MUX2(x0,x1,x2,x3,s2,s3)
  g2_y = MUX2(x4,x5,x6,x7,s2,s3)
  g3_y = MUX1(g1_y,g2_y,s1)
  y = g3_y
  return y

• Here is a simple call of MUX3 on a simple input.

#MUX3(0,0,0,0,0,1,0,0, 1,0,1)
MUX3(x0=0, x1=0, x2=0, x3=0, x4=0, x5=1, x6=0, x7=0, s1=1, s2=0, s3=1)

1

• In the next example we sample 3% of the truth assignments to the MUX3 input and check the output.

print("x0  x1  x2  x3  x4  x5  x6  x7  |  s1  s2  s3 | y")
print(50*'-')
for x0,x1,x2,x3,x4,x5,x6,x7,s1,s2,s3 in product([0,1], repeat=11):
  if random()<0.97:
    continue
  y = MUX3(x0,x1,x2,x3,x4,x5,x6,x7,s1,s2,s3)
  print(f"{x0}   {x1}   {x2}   {x3}   {x4}   {x5}   {x6}   {x7}   |  {s1}   {s2}   {s3}  | {y}")

x0  x1  x2  x3  x4  x5  x6  x7  |  s1  s2  s3 | y
--------------------------------------------------
0   0   0   0   0   1   0   0   |  1   0   0  | 0
0   0   0   1   0   0   0   1   |  0   1   1  | 1
0   0   0   1   1   0   1   1   |  0   0   1  | 0
0   0   0   1   1   1   0   1   |  0   1   0  | 0
0   0   1   0   0   0   0   1   |  1   0   1  | 0
0   0   1   0   0   0   1   0   |  1   1   0  | 1
0   0   1   1   0   0   0   1   |  0   0   0  | 0
0   0   1   1   0   0   0   1   |  0   1   0  | 1
0   0   1   1   0   0   0   1   |  1   0   1  | 0
0   0   1   1   1   1   1   0   |  1   1   0  | 1
0   0   1   1   1   1   1   1   |  0   0   0  | 0
0   0   1   1   1   1   1   1   |  1   0   0  | 1
0   1   0   0   0   1   0   1   |  1   1   0  | 0
0   1   0   1   0   0   0   0   |  0   1   0  | 0
0   1   0   1   0   1   1   0   |  0   0   1  | 1
0   1   0   1   1   0   0   1   |  1   1   1  | 1
0   1   0   1   1   1   0   1   |  1   1   0  | 0
0   1   1   0   0   0   0   0   |  0   1   0  | 1
0   1   1   0   0   1   0   1   |  1   1   0  | 0
0   1   1   0   1   0   1   1   |  1   0   1  | 0
0   1   1   0   1   1   0   1   |  1   1   1  | 1
0   1   1   1   0   0   0   0   |  1   1   1  | 0
0   1   1   1   0   1   0   1   |  0   1   1  | 1
0   1   1   1   1   0   1   0   |  0   0   0  | 0
0   1   1   1   1   1   1   1   |  0   0   1  | 1
1   0   0   0   0   0   1   0   |  0   0   0  | 1
1   0   0   0   0   1   1   1   |  0   1   1  | 0
1   0   0   0   1   0   1   0   |  1   0   1  | 0
1   0   0   0   1   1   0   0   |  1   1   0  | 0
1   0   0   0   1   1   0   1   |  1   1   0  | 0
1   0   0   0   1   1   1   0   |  0   0   1  | 0
1   0   0   1   0   1   0   1   |  0   0   1  | 0
1   0   0   1   1   0   1   0   |  1   0   0  | 1
1   0   0   1   1   0   1   1   |  1   0   1  | 0
1   0   1   0   0   1   0   1   |  1   0   0  | 0
1   0   1   0   0   1   1   1   |  0   0   0  | 1
1   0   1   0   0   1   1   1   |  0   0   1  | 0
1   0   1   0   0   1   1   1   |  1   0   0  | 0
1   0   1   1   0   0   0   1   |  0   0   0  | 1
1   0   1   1   0   1   1   0   |  0   1   1  | 1
1   1   0   0   0   1   0   0   |  1   1   0  | 0
1   1   0   0   1   1   0   0   |  0   1   0  | 0
1   1   0   0   1   1   1   1   |  0   1   0  | 0
1   1   0   1   0   0   0   1   |  0   0   1  | 1
1   1   0   1   0   1   1   1   |  1   1   1  | 1
1   1   0   1   1   1   0   1   |  0   0   0  | 1
1   1   0   1   1   1   1   0   |  1   0   1  | 1
1   1   0   1   1   1   1   1   |  1   0   0  | 1
1   1   1   0   0   1   0   0   |  1   0   0  | 0
1   1   1   0   0   1   0   1   |  0   1   1  | 0
1   1   1   0   1   1   0   0   |  1   0   0  | 1
1   1   1   1   0   0   0   0   |  1   1   0  | 0
1   1   1   1   1   0   1   1   |  1   1   1  | 1

3-bits Adder Design

• Here is a simple design for 3 bits adder with carry in (cin) and carry out (cout) bits

  

• This circuit acceps three types of input
  • two binary numbers: $(a_2,a_1,a_0)$, $(b_2,b_1,b_0)$
  • a carry in bit: cin.
• Its output $(y_2,y_1,y_0)$ is the binary sum of the two numbers (with the carry added).
• In case of addition overflow, we need a carry out (cout) output bit as well.
• The following PyCircPL code describes a model for the ADDER3 cell.

def ADDER3(a2, a1, a0, b2, b1 ,b0, cin):
    g1_y = XOR(cin, a0)
    g2_y = XOR(b1, a1)
    g3_y = XOR(b2, a2)
    g4_y = MUX1(a0, b0, g1_y)
    g5_y = MUX1(b1, g4_y, g2_y)
    cout = MUX1(a2, g5_y, g3_y)
    y2 = XOR(g5_y, g3_y)
    y1 = XOR(g4_y, g2_y)
    y0 = XOR(g1_y, b0)
    return cout, y2, y1, y0

• For example, lets try to compute 001+001

ADDER3(a2=0, a1=0, a0=1, b2=0, b1=0 ,b0=1, cin=0)

(0, 0, 1, 0)

This result should be of course interpreted as follows

cout=0, y2=0, y1=1, y=0

which is the correct result 10.

ADDER3(a2=0, a1=1, a0=1, b2=0, b1=1 ,b0=1, cin=0)

(0, 1, 1, 0)

ADDER9 - 9-bits Adder Design

• Here is a simple PyCirc Design Diagram for the standard 9-bits adder with a carry in (cin) and carry out (cout) bits.
• It uses 3 gates g1, g2, g3, of type ADDER3 which are chained by their cout/cin pins.
• Input: a<8:0> + b<8:0> + cin

• Output: y<8:0> + cout

  

• Here is a PyCircPL code for ADDER9:

def ADDER9(a8, a7, a6, a5, a4, a3, a2, a1, a0, b8, b7, b6, b5, b4, b3, b2, b1, b0, cin):
    g1_cout,y2,y1,y0 = ADDER3(a2, a1, a0, b2, b1, b0, cin)
    g2_cout,y5,y4,y3 = ADDER3(a5, a4, a3, b5, b4, b3, g1_cout)
    cout,y8,y7,y6 = ADDER3(a8, a7, a6, b8, b7, b6, g2_cout)
    return cout, y8, y7, y6, y5, y4, y3, y2, y1, y0

• Lets test this function withe the following input

ADDER9(a8=0, a7=0, a6=0, a5=0, a4=0, a3=0, a2=0, a1=0, a0=1, b8=0, b7=0, b6=0, b5=0, b4=1, b3=1, b2=1, b1=1, b0=1, cin=0)

(0, 0, 0, 0, 1, 0, 0, 0, 0, 0)

Advanced Topics -- To be Continued ...

• For the more experienced students we present here some more advanced features of the PyCircPL package will be added within the near future. To be contniued ...