CSC270 Lab 5

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--D. Thiebaut 13:39, 4 March 2009 (UTC)

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LAB #5: More Sequential Circuits

© D. Thiebaut, 2009

Part 1: Starting states, and Hard Reset

Setup

• Implement the 2-bit/4-state sequencer with the following equations:

D1 = Q1 xor Q0
D0 = not Q1

• Connect the CLR and PR to Vcc.
• Connect Q0 and Q1 to LEDs
• Verify that your circuit works when the 1Hz signal is connected to the CLOCK inputs.

Experiment

• Disconnect the clock inputs from the CLOCK signal, and connect them to GND. This way your sequencer is frozen and will not change state.
• Cycle the power OFF/ON a few times and record what state the sequence starts in. Compare with the sequencer of other people in the class. Do the sequencer always start in the same state? Why?

Hard Reset

• You are going to connect some of the CLR and/or PR inputs of the flip-flop so that you can always force (reset) the sequencer to be in State 10 (Q1=1, Q0=0).
• A single momentary switch should activate the CLR/PR inputs you selected.
• Reconnect the clock inputs to the CLOCK signal.
• Turn your sequencer ON and verify that you can always reset it by activating the momentary switch

Part 2: Controllable Sequencer

Implement and wire-up an UP/DOWN 2-bit counter.

An up/down counter is a counter with an outside control signal, UP/DWN' which, when 1 forces the counter to count up, i.e. its outputs go 00, 01, 10, 11, 00, etc. When UP/DWN' is 0, the counter counts down, i.e. its outputs go 00, 11, 10, 01, 00, etc.

Add a CLR' outside signal that will allow the user to clear the counter asynchronously, forcing its two bits to 0 0.

Part 3: Up-Down LED display

Do not disconnect your Up/Down counter, and connect its Q outputs to a 2-to-4 decoder. Connect the 4 outputs of the decoder to 4 LEDs and make the LED pattern go LEFT or RIGHT depending on the UP/DWN' signal.

Be imaginative when it comes to using/finding/creating a 2-to-4 decoder!!!