Up/Down Counter Not Counting Down

[TheRedDevil18]

Homework Statement

I'm trying to build a 2 bit counter using JK flip flops. In the simulation it counts up just fine, but when I switch it to count down, it starts at 3 and then goes to zero and counts up again.

Homework Equations

The Attempt at a Solution

[/B]
Here is my circuit diagram:

When the switch is closed it should count down, and when it's open, it should count up. The clock is connected to a 555 timer, just didnt show it.

 

[berkeman]

Homework Statement

I'm trying to build a 2 bit counter using JK flip flops. In the simulation it counts up just fine, but when I switch it to count down, it starts at 3 and then goes to zero and counts up again.

Homework Equations

The Attempt at a Solution

[/B]
Here is my circuit diagram:
View attachment 105174

When the switch is closed it should count down, and when it's open, it should count up. The clock is connected to a 555 timer, just didnt show it.

I'll look more at this, but could you post your design equations?

 

[TheRedDevil18]

I'll look more at this, but could you post your design equations?

Y = M'Q + MQ'

Where Y is the output, those AND and OR gates.
M is the control input (switch), it counts down if M = 1 (closed switch) and up if M = 0 (open switch)

And the flip flop in the simulation is a 74HC112

 

[Tom.G]

Your circuit is using the JK flip flops as T flip flops. Look them up; T flip flops change state on every clock cycle.

 

[LCKurtz]

If you want a synchronous machine, wouldn't you want the clock inputs connected only to the clock?