There is an old puzzle in which a farmer must transport a wolf , a goat , and a cabbage across a river. However, the farmer can only transport one of , , or across the river at a time, and if left together and unattended, the goat will eat the cabbage and the wolf will eat the goat. Let indicate the presence of the farmer on the west bank of the river and indicate presence on the east bank. Use similar definitions for , , and .
I expect that you will be able to complete this work during normal lab time. Please show your work to me or a mentor after each step in the lab work section below. If you are unable to finish all of the steps below during our scheduled lab, you may save your circuit on the board. Once you have completed the lab, schedule a time during my office hours where at least one member of your group can demonstrate your completed lab and show
TTL chips look approximately like this. They are 14-pin “dual in-line packages” (DIPs), meaning that the chips are long and narrow with 7 pins on each side. Each chip has a small notch in one end for orientation. When the notch is pointed upward as in the diagram, the pins are numbered from 1 to 14 starting in the upper-left corner and proceeding counter-clockwise.
For purposes of your logic design, note we have the following TTL chips available in the lab:
I will provide a pinout diagram, showing what each pin on each chip is for. Please note that the pinout for different chip types (AND, OR, etc) is different.
Please note carefully, that you must connect each chip to power and to ground. It is important that you use the correct pins for this. Reversing power and ground will damage the chip. Make sure you connect to +5v and ground, not the adjustable +v or -v rows.
Please refer to the protoboard diagram provided in the lab handout, to locate the “channel” between banks of pin connection points. To seat a chip in the protoboard, orient it such that its notch is facing upward as in the diagram, then place its two rows of pins such that they straddle one of the valleys in the board. This helps you attach power and ground to the correct pins, and ensures that none of the pins are connected together.
The chips may take some careful coaxing to seat them properly. I suggest placing one row of pins loosely into their holes in the board, and then using a fingernail to get the other row of pins lined up and started into their holes. Once all pins have been started correctly, you can press firmly, and the chip should snap into place. (Please be gentle until the pins are started well, or they will get bent, but then do press firmly to make sure the chip is fully inserted and that each pin makes a good connection with the board.)
Be careful not to pull chips out of the board at an angle, which could bend or break the pins. Grab the chip at the top and bottom edges (where the chip crosses the channel on the protoboard). If you cannot remove the chip by hand, we can remove it carefully using a small screwdriver.
Now that we’re working with TTL chips and the logic switches in the lower left corner of your protoboard, you can safely omit resistors from your circuits. Instead of turning the circuit on and off, logic switches make a connection from your wire to either +5v or ground. That eliminates the need for pull-down or pull-up resistors. The other use case for resistors in our previous lab was to limit the current through transistors and LEDs. As long as you use the logic indicators on the right side of the board instead of raw LEDs, you can omit these resistors as well.
Please double-check to make sure your logic indicator and logic switch sections are set to TTL mode. While you’re double-checking your board configuration, make sure your TTL chips are powered from +5v and ground, not the adjustable +v or -v rows.
Based on the fox, goose, and bag of beans puzzle.