USR error in Altirra 3.00

[Ranger03]

code:

let a=usr(550)

Data 324,400,123

Data 213,123,40

data 123,12,23

end

a=usr(550)

then a menu popped up and said that the emulator had jammed

[phaeron]

What are you trying to do? USR() invokes machine code that you've copied beforehand to the given address. Address 550 isn't a valid address for USR code, it's in the middle of the OS variables.

[Ranger03]

did the author test 3.00? i can't run anything

[phaeron]

I'm pretty sure he tested it, yes. The BASIC code you have in the original post doesn't make sense and will crash on any Atari computer. If you're trying to type in a BASIC listing from somewhere, it would help to have a link so we can see the original listing or article.

[Mclaneinc]

Ranger, consult books like Mapping the Atari which are all over the place including if memory serves on MrFish's super fine web site http://seriouscomputerist.altervista.org/

 

It will show you where is and isn't in this case a good place to store code...

 

And yeah, I think we can assume the author tested your code in this case

 

If you have not looked at that book before then do, its a bible for programmers with the odd mistake that the author of Altirra has noticed, in fact you may want to check out this:

 

http://www.virtualdub.org/downloads/Altirra%20Hardware%20Reference%20Manual.pdf

 

Its the Altirra hardware reference manual, another MUST HAVE book...

 

I forget the authors name..

 

He seems to know his stuff though..

 

 

Have great fun with your programming

 

Paul..

Edited July 22, 2018 by Mclaneinc

[Ranger03]

i never bothered to complete the program anyway, but it's still somewhat perplexing.

 

it went something like this:

 

rom=8155

ram=8255

fori=8122 to 8255

poke ram+i

peek(ram+i)

 

or something like that, can't remember.

[Ranger03]

What are you trying to do? USR() invokes machine code that you've copied beforehand to the given address. Address 550 isn't a valid address for USR code, it's in the middle of the OS variables.

so is that what the rem statement is for? to copy machine code?

[flashjazzcat]

There's some useful reading for those wanting to learn Atari BASIC (which appears to be what you need to do first) in this thread:

 

http://atariage.com/forums/topic/257073-i-need-some-suggestions-for-good-beginner-basic-books/

[Kyle22]

code:

let a=usr(550)

Data 324,400,123

Data 213,123,40

data 123,12,23

end

a=usr(550)

then a menu popped up and said that the emulator had jammed

 

First of all, there is no need to use the word LET.

Second, if you would try it, LET USR does the USR call immediately. Jump into Atari BASIC and type: LET A=USR(58487).

Instant jump through $E477.

 

As mentioned above: 550 is NOT a proper address for your own code. That area is reserved for the OS Timers.

 

Try $600 (1536).

 

Please Read several times until you understand Mapping the Atari: https://www.atariarchives.org/mapping/memorymap.php

[Heaven/TQA]

And those 324,400 are not suspicious???

[Kyle22]

How did I miss that??? Of course, only 0-255.

 

Also, you would need a for...read...poke...next loop to load RAM with your data before the USR call.

[kenjennings]

Ranger03:

 

Some simple utilities in assembly language for Atari BASIC:

 

http://atariage.com/forums/blog/576/entry-13175-part-1-of-11-simple-assembly-for-atari-basic-introduction/