This lab exposes the student to the use of various register configurations. First, a register and shift register are built from individual D flip-flops, and then a 7495 shift register is used to perform the same function. Finally, 4-bit serial communication is implemented using two 7495 shift registers.
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1. Using 7474 D flip-flops, wire a 4-bit register similar to the one in Figure 10.1. Connect the inputs to switches on the D/A trainer and the outputs to the LEDs. Using a pulser switch as the clock input to load data, store several values in the register. Does the output change when the inputs change or on the clock edge?
2. Using 7474 D flip-flops, wire a 4-bit serial-in parallel-out shift register similar to Figure 10.2. Connect the clock input to a X switch. Data is loaded 1 bit at a time by setting the switch to the desired value and pressing X to load the value into the most significant bit of the register. Repeating this four times loads a 4-bit value into the register.
3. The 7495 shift register can perform both serial-in parallel-out and parallel-in serial-out operations. Noting the use of the mode control to clock inputs from the data sheet for the 7495, use the 7495 to perform the same function as in 2).
4. Use two 7495's to perform serial communications. One is used to parallel-load data from the switches and send the value serially, while the second is used to serially receive the value and display it in parallel on the LED's. Note carefully the transmit-receive sequence as outlined in Section 10.2.2. Produce a logic diagram and wire and test your circuit. (Hint: To clock the two registers, connect the output of X to the clocks of the transmit register and then invert this signal for the clock of the receive register. This way, the transmit register is loaded or shifted when the X is pushed, and the receiving register loads the data when X is released. Note carefully on which clock edge the 7495 triggers, and from this insure that the transmit register gets the proper clock edge first.)
10.1, 10.2