Memory test

[savage]

Hello forum,
I'm trying to get my version of Memory.hdl to work, but to be honest, after three days of thought I'm no further forward.
I have the RAM16K section working but cannot figure out how Keyboard and SCREEN are supposed to fit in.
I understand that these have their own area in memory - does one need to somehow refer to them separately depending on the address being dealt with?
Any idea to focus on would be great - just something to get me kick-started again.

Cheers
Savage

[ybakos]

Did you notice the diagram in chapter 5?

[cadet1620]

If you look at figure 5.7 and ignore the wires heading to/from the screen and keyboard, doesn't it look a lot like one of the RAMs—parts with smaller address spaces combined together to make a larger part?

The tricky bit is that the address space is not evenly divided amongst the internal parts so it takes a bit more logic to route data and load than it took in a RAM.

--Mark

[savage]

Hello Ybakos and Mark,
Thanks for your comments - they did enable me to start thinking again. Two things puzzle me though:
Firstly, since addresses in the screen memory are 15 bits, why does the inbuilt screen chip only specify 13 bits?
and secondly, after I find that the address refers to the keyboard memory map, I'm stuck for a way to  get it into the Keyboard chip.

Thanks

Savage

[cadet1620]

[Replied directly to savage.]

--Mark

[baylorfan]

cadet1620 wrote

If you look at figure 5.7 and ignore the wires heading to/from the screen and keyboard, doesn't it look a lot like one of the RAMs—parts with smaller address spaces combined together to make a larger part?

The tricky bit is that the address space is not evenly divided amongst the internal parts so it takes a bit more logic to route data and load than it took in a RAM.

--Mark

So I am trying to deal with the routing between the RAM16K and the SCREEN chips via a simple DMux, by connecting the MSD (address[14]) to the 'sel' in the DMux chip.  For some reason — possibly a typo I cannot detect? — I cannot even get my Memory.hdl to load.  The stated error is "A pin name is expected."

Any assistance is appreciated.

[cadet1620]

baylorfan wrote

So I am trying to deal with the routing between the RAM16K and the SCREEN chips via a simple DMux, by connecting the MSD (address[14]) to the 'sel' in the DMux chip.  For some reason — possibly a typo I cannot detect? — I cannot even get my Memory.hdl to load.  The stated error is "A pin name is expected."

Any assistance is appreciated.

If you email me your HDL I'll be happy to take a look at it for you.  (More > Reply to author)

--Mark