tristate_values.py

from random import randint
from myhdl import *

# output from the following tristate example
# Driver1  Driver2  Tristate  
#  None     None     None
#  None     1        1   
#  0        None     0   
#  None     1        1   
#  1        None     1   
#  None     1        1   
#  1        None     1   
#  None     1        1   
#  0        None     0   
#  None     1        1  

def tristate_values():

    tri = TristateSignal(bool(0))
    dr1 = tri.driver()
    dr2 = tri.driver()

    #def _stim():
    @instance
    def tbstim():
        print("Driver1  Driver2  Tristate  ")
        for ii in range(10):
            print(" {:4}     {:4}     {:4}".format(
                str(dr1), str(dr2), str(tri) ))

            if (ii % 2) == 0:
                dr1.next = None
                dr2.next = randint(0, 1)
            else:
                dr1.next = randint(0, 1)
                dr2.next = None
                            
            yield delay(1)

        #return tbstim

    Simulation(tbstim).run()


if __name__ == '__main__':
    tristate_values()