Now that we have 1 bit of memory, it’s pretty simple to build that into something more useable. By putting 8 D Flip Flops together we get 1 byte of memory. If we double that and add an address bus, we get 2 individual bytes of addressable memory. I could go on but I think two bytes is enough to demonstrate usage of both the data and the address buses.
The address bus is simply 1 bit in this example. 0 means we’re addressing the top 8 bits of data, 1 means we’re addressing the lower 8 bits of data. Doubling this and having 4 lines means 00,01,10,11 or 2 bits of addressable memory, each of which is 1 byte (8 bits).
Typically you would control the read/write* with only 1 bit: 1 means read, 0 means write, but for clarity I have two data buses here: one for input (the 8 bit bus on the bottom of the diagram), and one for output (the 8 bit bus on the top of the diagram).
On the bottom left I have some non-relevant components that I used for testing the 2 bytes of memory. The clock is obviously necessary, but the rest are: a Logisim random number generator (8 bits) to fill the addressed 1 byte of memory for testing, and a 8 bit LED output for testing the output data bus. There are 3 1-bit controls: an on/off for the clock signal, the read/write* control bit, and the 0th / 1st byte switch for testing the address bus.
2 Bytes of RAM from D Flip Flops