Part A: Design a BCD $($Binary Coded Decimal$)$ counter that counts from $0,1,2,..\mathrm{.}9$ then goes back to $0$ and repeats. Using D flip$-$flops in this sequential circuit.

Each clock cycle, the counts will increase by $1$; when it reaches $9,$ it will go back to $0$ next clock cycle and repeat the process.

Design Procedrue:

$1.$ Draw the state diagram of the is BCD counter.

$2.$ Fill the state diagram below. $($Left column represents present state, and the right column represents next state$)$

BCD counter state table.png

$3.$ Based on the stable table above, draw Karnaugh maps to find boolean expressions for each D flip$-$flop's input $($i$.$e$.$ D$3,$ D$2,$ D$1,$ D$0)$ in terms of Q$3($t$),$ Q$2($t$),$ Q$1($t$),$ and Q$0($t$).$ Mark the inputs$/$minterms from $1010$ to $1111$ as don$$t care conditions in K$-$map.

$4.$ Draw the circuit at gate level using logicly$.$

draw the next state logic using logic gates based on the $4$ boolean functions from step $3,$ label outputs as D$3,$ D$2,$ D$1,$ D$0.$

place $4$ D flip flops.

Connect all the PRE' of $4$ D flip flops with a toggle switch. Connect the CLR$\text{'}$ of $4$ D flip flops with another toggle switch. Set both switches to HIGH.

Don't forget to name the toggle switch in the field of "Export name" of the "toggle switch properties" pop up panel:toggle switch.png

Then connect each output of next state logic to each input D of D flip flop, respectively.

Drag and clock from the left panel and place on the circuit. Connect the clk signal $">"$ of all the $4$ D flip flops with the same clock input.

Drag the $"4-$digit" display from the left panel.

$4$bit digit$-2.$png

Connect the output Q of $4$ D flip$-$flops to the inputs of this $4-$digit display appropriately.

Note the top input of the $4-$digit display is for the lowest bit and the bottom is for the highest bit. So connect bit $0$ to top, then bit $1,$ bit $2,$ and bit $3$ on the bottom input, in order to display $4-$bit binary in decimal correctly using this $4-$digit. fix my logic gate using logic.ly please