Figure 8.23. There are 4 flip-flops labeled from left to right, FF eh, FF B, FF C and FF D. A terminal labeled eh input goes to the Ck input of FF eh. The Q output goes to a terminal labeled Q eh. There is no other connection to FF eh. Another terminal labeled B dash D input goes to the Ck inputs of both FF B and FF D. The Q output of FF B goes to a terminal labeled Q B. This Q output also goes to the Ck input of FF C. The Q output of FF C goes to a terminal labeled Q C. The Q output of FF D goes to a terminal labeled Q D. The not Q output of FF B and the Q output of FF D go to the two inputs of a NAND gate. The output of this gate goes to the J input of FF B. The Q outputs of FF B and FF C go to the inputs of an AND gate. The output of this gate goes to the J input of FF D. Below the diagram is the legend, quote, For normal B C D operation Q eh is tied to the B dash D input. Below the legend is a truth table which has the columns Q eh, Q B, Q C, and Q D. The rows are as follows. 0 0 0 0, 1 0 0 0, 0 1 0 0, 1 1 0 0, 0 0 1 0, 1 0 1 0, 0 1 1 0, 1 1 1 0, 0 0 0 1, 1 0 0 1, 0 0 0 0. End verbal description.
Go back.