Hi there. In this video I am going to take
the 1 bit of memory we created and produce 1 byte of memory. We have the CPU_MEM_1 in
here and we can place it up here and I can take 8 instances of this. Using ctrl v for
copy and finally copy the four to give 8. Now we have 8 instances. We are going to have
an input. We want an 8 bit input pin so we choose a splitter. Which will give us just
one port with 8 pins. Now we can connect this up, we will face it south first and this one
as well. So we now connect the inputs and outputs to the splitter. 0 ,1,2 ,3 ,4,5,6,7.
Now we have to be careful to make sure we connect to the correct splitter ports. So
0 is at the far end and we connect the rest. 1 ,2,3,4,5,6,7. So we then get an input pin
facing east and it is an 8 bit pin and we can call it i for input. Now we can place
the output pin facing east and call it o for output. You notice that the inputs are at
zero and the output is sitting at an error value , as we see the error in the lower level
as it does not know what value to take as we have a race condition. If we go to main
and connect all the sets together. So in effect the set will set the byte to memory. Now add
an input pin at the bottom and it is a 1 bit input and face it north and we can call it
s for set. So our circuit is now built. The way it should work is if we change the set
to a 1 it will pass through whatever is in the input to the output. So all the zeros
should pass to the output. There you go. All the zeros are passed through. It means that
this input is now transparent and passes straight through to the output. So if I change any
of the input values you will see the output changing. So this is a check on the working
of the circuit. Everything is working. So when I take the set to low then all the output
values are fixed, so this wire is fixed at the high level and we can see the wire in
the lower level is fixed. If I was to change any of these inputs although the inputs change
the output does not change so this is an 8 bit memory and the input is passed through
in a parallel fashion by the set bit. Now we can go in and create a hierarchy . So let’s
create a circuit and call it CPU_MEM_8.now we can go in to main and cut and paste the
circuit into CPU_MEM_8. now we can edit the circuit appearance and change the look of
the circuit. Draw a new rectangle and move the pins and delete the old rectangle and
name it CPU_MEM_8 so we now have 1 byte of memory. So we can go in to main and pick up
the 1 byte of memory and place it. That is all for this video.
In the next video we will add a little enable section onto this. So the set will set the
value into memory but we need to be able to enable it onto a bus. So we add a little enable
section. We will look at that in the next video and probably the decoder as well. Ok
thany you and goodbye.

8 BIT CPU 8 Bit Memory

One thought on “8 BIT CPU 8 Bit Memory

  • June 1, 2018 at 8:59 pm
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    I'm reading the book "How does it know it" – And your videos is helpinh me a lot to understand some parts of the book. It's good to know, people like you, use the internet for the benefit of education. Thanks a lot!

    Reply

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