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Step 1: The Stuff You Need to Have or Get
Its a much shorter list this time:
8 74hc00 or 74hct00 Quad NAND Gates. For the circuits used in this instructable, only these chips will work.
8 4.7k -10k resistors
8 small signal diodes - the common 1n4148 variety works well
A breadboard with at least 63 rows, or you will need more than 1.
Wire - it helps to connect things (you think: Is he for real here?)
Wire Cutters - (you already think: Let Me Guess...) Yup, they make cuttin' wire so nice!
Needle Nose Pliers - optional, but i find them nice for bending and placing wire.
8 Resistors (that work with the LEDs)
Step 2: Chips and Breadboards
With self contained ram bits, it is a lot easier putting them onto the breadboard. This is very opposite of the TTL RAM, which was complicated enough that you had to go transistor by transistor. The CMOS RAM was easier to place, but it was very large and cumbersome, so we only made 1 bit (that and it used all of my MOSFETS).
Basically, all you need to do is line the chips up down the board, and keep them oriented the same way.
Step 3: Wiring the Chips
The wiring diagram should be easy to follow. The red lines that connect the pins are wires that you need to place on each chip. You do not need to place wires leading out on the D, CLK, Q, and NOT Q. I would recommend connecting you ground and supply pins to the rails though.
This configuration will not work with the 4000 series, because of conflicting pinouts, but for those of you who are going to comment and say "Can I use the 4011?" Or insert another 4000 series NAND gate there. I have provided the D latch schematic. You can find a 4011 datasheet and do it yourself.
Step 4: The Diode and Resistor
What we are going to do is add a diode from the Q pin (either 10 or 11) to a free row on the breadboard. The black strip on the diode should be toward the free row pin. If it is toward the connection to the Q pin, it needs to be flipped around. Now you need to connect the diode to the Data input pin (pin 1) using the resistor. Repeat for all 8 chips.
Step 5: How It Works
In order to use the same pin to send and receive data, we had to add a resistor and diode between the Q and Data signals. We needed the diode because the latch can be affected by changes on the Q pin and diodes, as you know, only let current go one way, in this case, from Q to Data. The resistor was needed to limit the current going from Q to Data. Without it, the latch would get messed up, because Q would be pulled to ground.
Step 6: Interfacing to Your Microcontroller
*The RAMRead() function does not work right when the chip is on the board because pins 0 and 1 are attached to the FTDI chip, which messes up the reading.
Have Fun Saving a byte of internal Micro RAM!!