Why do you have connected the ouput of the 555 timer to the inputs A-D of the 74LS193 instead the UP (or DOWN) input clock?
Why the value of R1 and R2 is 100R? You need to adjust the parameters to satisfy [imath]R_1,R_2 \geq 1k\Omega[/imath]
If you want the timer to oscillate a certain frequency then use the "555 timer wizard". In multisim go to Tools > Circuit Wizards > 555 timer wizard. apparently you are using it but you changed the values.
What is the circuit supposed to do? You did not specify that. Is it a 0-9 counter? Because 74LS193 is a MODULO-16 Binary counter.
When the output of the 555 timer is high, then the inputs A-D are also high, i.e., A=1, B=1, C=1 and D=1. With this, each output may be preset to either level by entering the desired data at the data inputs
while the load input is low. But in your case, the LOAD input (pin 11) is
always LOW, you need a pulse instead. There will be no force in the universe that will be able to change the output of the 74LS193 if the LOAD pin is always LOW.
