This instructable I'm going to show you how to make a RAM to use with a micro-controller for storing data and it is also expandable and uses only one IC and no other components. It is easy for any hobbyist to make.
Step 1: The chip
The chip is a ten bit decade counter the "4017" but we only use two bits. You will make only six connections. Here is the data sheet of the chip.
Step 2: The schematic
Wire every thing as the schematic.
Step 3: Using it
To use it on a micro-controller (for example arduino or pic )the read pin is connected to digital pin on the controller and the digital pin is set as an input. The write pin is connected to a digital pin that is set as an output. The write enable is connected to a digital pin that is set to output. When the chip is turned on for the first time the read pin is high. To write pull the write enable pin low then if the read pin is high a pulse will make it low if it was low a pulse will make it high. (what i mean here by pulse is pulse going to the write pin). If you don't want to use it with a micro-controller then connect a 4.7kohm resistor between power an write enable pin.
Step 4: Expanding
To add more bits or if you go large bytes (1 byte = 8 bits) duplicate the circuit as many bits as you want and then connect all the write enable pins together.
Source: Taken From Internet, Use on your risk.
