Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

How Computer Memory Works
...
These are just
used to process or combine various inputs, but if we connect them in a specific way, we can
actually get them to store information at least until the power is turned off
...
An OR gate is on when either of its inputs are
on, or both of them are on
...
So often you'll get books
like this which will give you details of different things
...
The AND gate, the 7402, has the inputs on pin
two and three and the output on pin one
...
And these are
called NAND gates or nor gates
...
They have two inputs
and they have them together but immediately following that, build into the chip, is what is called
a NOT gate
...
Its output is off when both of its inputs are on
...
A NOR gate has two inputs and it has
an output which we'll label as A and B
...
Normally with an
OR gate, zero or zero would be zero
...
Take a look at the circuit that we used over there
...
And we've got the inputs to these like so
...
And I'm gonna label the first one q and the other one we're gonna call this not q
...
We've still got zero and
one as the input here, so now we know that the output of q bar is zero
...
The output of not q prime is one
...
So it
stays the same, and you get the same input coming through
...


Flip Flops, Latches & Memory Details
...
Today, we'll look
at how to take this further and see how computer memory is built in more detail
...
We need to think of some circuit that is true
for both S when both D is 1 and CLK is 1
...
With the D flip-flop we can store a single bit of information, but often on a
computer we want to store more than that
...
Each wire stores one bit so one wire stores
"bit 0," one wire stores "bit 1," and so on
...
We're going to use four bits here just because it saves on drawing
...
There are 8 chips on the sim used to store multiple bits
that are stored in parallel
...
So that's
how we can store 8 bits whether a byte or a word, we just have 8 single bit "things" in parallel
...


In our previous video on how memory worked we got to the point from storing one bit of
information that we could set or reset it to the flip flop where we could store a bit of info and then
we arranged for them together in parallel to store four bits of information so what we did we had
four inputs d naught 2 d 3 which gave us our input and four outputs q naught to q 3
...
Now I want to be able to access either
this one or this one
...
The NAND gate has two
inputs, a and b, and an output, which again will use q
...
When
the input to the knock cage is 0, the output is 1
...


Archimedes would run reliably above 100 degrees Celsius this is just the half adder we want a
binary full
...


Total Recall (Memory Addressing Pt2)
...
But what about reading
...
We have our two inputs A and B and our output q
...
The way we do that is by using an OR gate
looking at the inputs like that
...
We have a grid effectively of cells where we
can store our data , and then again we have the multiplexer is using all gates to combine them
together to produce output and then we can stack these in 3d to produce the sort of 8bit outputs
like I've got here

---