Re: Oscilloscope
The design steps are:
1) get the counter to work. You want a 2-bit output. The 2-bit output has four counting states: 00, 01, 10, 11. Sounds like you have this already if you use the D flip flop.
2) Use a diode and a series resistor R, to connecto to Qa output. This is you MSB current offset. Use a second diode ans a series resistor R, to connect to Qb output. This is your MSB current offset (1/2 the size of the first one). Sum those two offsets, plus your input signal, to give the (input + offset)--in 4 different offset flavors.
3) Use some sort of multiplexing circuit using QA, notQa, Qb, notQb to select one of the four input signals as a function of the 2-bit count input. You have to grind thru the logic to make sure the inputs are selected one-at-a-time.
THen you are done.