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I was under the impression that you had already started.Marks256 said:Let's not start the "PICs are better" thing. Ok? I will start with PICs when i feel that i am good and ready.
blueroomelectronics said:Hey Marks256, here's a ZX81 clone schematic (yes Z80 with video)
**broken link removed**
http://oldcomputers.net/
tkbits said:At any rate, I would prefer you learn the simple and common things, before learning the complex and rare things.
I think that's why Marks256 wants to play with the z80. Not very practical, but much more "fun" for him than a PIC. People build tube amps. Why not vintage computers? It's a hobby for most of the people here.the fun is leaking away.
That's pretty much how most keyboards work; a scanned matrix of keys.Marks256 said:some sort of scan system goes through (demux?) each individual line looking for keys that are on or off. that way, if two keys are pressed in one row, and one in another, the device won't get confused. this way, only ONE "row" has it's data being read. not the whole keyboard at a single given time...
kchriste said:I think that's why Marks256 wants to play with the z80. Not very practical, but much more "fun" for him than a PIC. People build tube amps. Why not vintage computers? It's a hobby for most of the people here.
kchriste said:That's pretty much how most keyboards work; a scanned matrix of keys.
One byte or nybble at a time. Check out instructions that set and use the carry flag.Marks256 said:..
Another question. How does an 8 bit processor handle numbers larger then 255?
Papabravo said:One byte or nybble at a time. Check out instructions that set and use the carry flag.
kchriste said:Its handles larger numbers the same way you do when not using a calculator. ie: When doing addition on paper, you will only deal with single digits at a time and use "carries" to move the values in excess of 9 to the column on the left:
56 + 37 =??
6 + 7 = 13
So keep the 3 in the units column and add the 1 to the 5 & 3 in the 10s column ( 5 + 3 + 1carry = 9 ) so the answer is 93. The 8 bit processor program has to do the same thing except it only has to carry when the answer exceeds 255 (For unsigned math) or 127 (For signed math).
Funny thing on this topic is that I only really learned math once I started writing assembler: I'd never thought about the fact that multiplication is just a form of addition. ie: You can figure out 7 x 13 just by adding 13 to itself 7 times. Too much emphasis on just memorizing multiplication tables when I was growing up I guess.
Marks256 said:Does anyone know of any books (free would be nice... as in ebooks, but not a requirement) that i can get to read up on z80 Assembly? I understand what most of the op codes do, but there are a few that i can't figure out what their purpose is...
Marks256 said:Does anyone know of any books (free would be nice... as in ebooks, but not a requirement) that i can get to read up on z80 Assembly? I understand what most of the op codes do, but there are a few that i can't figure out what their purpose is...
Nigel Goodwin said:If you don't understand it, you probably don't need to know about it - a 16F PIC has only 35 instructions, and probably a third of those are only very rarely used (some I've NEVER used!).
As always, build one, and play with it - rather than keep asking silly questions!.