AVR Freaks

Bill,

Thanks for providing the hex files. Now I need to order some ATM328 chips, and get this current job off my back, then I can sit down and have a play.

Thanks again,

Zadok.

PS Regarding your point about tokens:

I guess the reason why I am a bit "obsessed" with tokens, is that I so often use the assembler code:

mov ZL,Command
icall

To execute code based on the contents of a byte, that I must want to do it for everything. It takes 3 instructions and 6 clock cycles to get there and I like this! (Another 2 cycles and one instruction because of the intermediate jump table).

[Note: This code works if the jump table is on a 512 byte boundary - 256 words, ZH contains the high address.]

So if there were tokens in the EEPROM (or Flash) it would mince through them like lightning. Well, I know, that's the *easy* part, the tough part is making the language work, but then you have already done that...

[Although I don't know how this is implemented in C for the AVR, I should think a similar sort of construction is used]

With 256 unique codes, there would probably be enough for all the basic functions, operators, use maybe a-z and / or A-Z letters as variables and so on.

Of course, I again have to say that I haven't written a language or a compiler so this is just hot air from me.

It was interesting to read about the old ZX80 home computer that someone in our earlier thread referred to, it only had 1K RAM, but because it used tokens, apparently you could even get a chess program (of sorts) into it!

So I guess that just goes to prove your point that you don't need space for 1,000 instructions in a system of this sort. From a marketing point of view though, people are nowadays used to such absurd amounts of memory that our world of microcontrollers leaves them aghast that anyone could do anything in such a tiny space. So I think most people who were looking at buying something like a single chip computer would be a lot happier to be able to read something like "a maximum of 1,000 program statements" rather than "1K byte of program memory" if you see what I mean.

So, just wanted to say why I'm secretly hankering for tokens, even though as you say, and as the chess program example illustrates, it doesn't really matter!

Bill, I've been thinking about compilers and stuff and now (I think) I understand...

There's no point having a token type interpreter with source code as well, at least in an AVR there's not enough RAM for both. As the whole point of tokens is to save RAM, it's pointless unless you interpret and store each line of code as p-code as it's typed in.

This leads to interesting problems with resolving forward address references and loops, and means editing is a whole new challenge. Plus listing the program needs a decompiler as you said above.

Yes, I've been thinking about it. I'm just one of those people who has to understand before he can use something, so now the penny has dropped, I can get on with it.

I've ordered a couple of ATM328's so they should turn up next week some time.

Thanks for bearing with me while my brain cells do their thing (albeit slowly).

Zadok.

On the old ZX80 there must have been a kind of compiler / interpreter as it stored programs as tokens (which I equate to p-code) in the precious 1K of memory. Must have been pretty hairy software in the ROM, or maybe it used some tricks to keep the job simple. No labels for a start I would imagine.

They're a rare item these days. I wonder if anyone has the Z80 source code for the software.

Z.