Well, I've been busy playing with my logic chips and an 8bitbaby (which is a generic retro interface card) and the Plus/4. I'm currently trying to map a small range of I/O addresses ($FE00-$FE7F) to a LED.
That is, whenever this address range is accessed, the LED should light up - in theory anyway.
After fixing it several times - mainly because the IC diagrams were confusing, particually as I was wiring the thing upside down! I'm getting more and more respect for folk that have been doing this for years, it takes a really steady hand and serious dedication as you have to quadruple check things to make sure its all working! (not to mention follow messy wires all over the place)
![](https://2.bp.blogspot.com/_4u8cCnKjBs4/RZ2eHRYNQwI/AAAAAAAAABU/yLIHliUMPZ0/s200/led1.jpg)
This is my first real attempt at actually building a whole circut that I've designed, away from a breadboard and its taken ages! I think what I really need to do is build an interface that I can hook-up to a breadboard; things will go a lot faster if Im not soldering all the damn time!
However, all that said, it does actually work! If the program hits locations
$FE00 to
$FE7F, the LED comes on!! How cool is that!
This is the reason I wanted to learn electronics in the first place, so I could build cool little add-on's. Now I know a memory mapped LED isn't exactly exciting, but if I add an octal flip-flop (which gives me 1 byte of memory) and enable it on write access, I can then use this to drive the LCD screen! This means I could have a memory mapped LCD screen expansion card! Now that is cool!!
![](https://1.bp.blogspot.com/_4u8cCnKjBs4/RZ2kcBYNQyI/AAAAAAAAABs/lDfhybUgk_g/s200/led3.jpg)
Oh...and I also see why people use GAL's everywhere now; they are ideal for this kind of thing! I have a couple ordered, but no sign yet..... and although my EPROM programmer can write to them, I have no software that builds the binary file TO write to it?!?!?! So I've not a clue how to physically use them yet! This image shows the logic I've used... which is also why its a bit ugly. I guess I could use an EPROM instead of a GAL for now....
Edit: Oh...and looking at that diagram, yes...I
really need to get some basic AND and OR gates!
2 comments:
Jeez, plz someone save Mike from the hardware hell!
BAH! Not hell! Fun fun fun!!!
Post a Comment