6502 Memory Map resource?

[JohnnyRockets]

Hi all,

 

I am playing with ASM on the 6502 (with simulator), but the simulator I'm using uses memory locations $0200 to $05ff to draw to screen.

 

I started to wonder, is this typical? In order to write to the screen, what memory location(s) are standard (typically)?

 

Also, what is the best resource to better understand the Memory Map? I have A LOT of 6502 books on PDF, but was wondering if one book "kind of rose above" the others for this purpose?

 

 

Thanks,

 

 

 

JR

[+SpiceWare]

The only "6502 Memory Map" is:

 

$00-ff = zero page

$100-1ff = stack

$FFFA-FFFB - NMI vector

$FFFC-FFFD - RESET vector

$FFFE-FFFF - IRQ/BRK vector

 

The position of everything else depends where the manufacturer mapped the components (RAM, video, sound, timers, io, etc) to.

 

One thing that might confuse you about the above is that in the case of the 2600, Atari did an addressing trick that maps the same 128 bytes to both 80-ff and 180-1ff. In other words, zero page and the stack share the same memory even though the 6502 thinks they are different - data you write to memory location $80 can be read from location $180.

[JohnnyRockets]

The only "6502 Memory Map" is:

 

$00-ff = zero page

$100-1ff = stack

$FFFA-FFFB - NMI vector

$FFFC-FFFD - RESET vector

$FFFE-FFFF - IRQ/BRK vector

 

The position of everything else depends where the manufacturer mapped the components (RAM, video, sound, timers, io, etc) to.

 

One thing that might confuse you about the above is that in the case of the 2600, Atari did an addressing trick that maps the same 128 bytes to both 80-ff and 180-1ff. In other words, zero page and the stack share the same memory even though the 6502 thinks they are different - data you write to memory location $80 can be read from location $180.

 

Oh, okay, so it is different for the Atari and different for the C64 and different for the, etc...

 

So if I want to write/print to the display, it will be different memory locations depending the the machine, right?

 

Sorry, this probably is SO darn basic and newbie-ish, but I'm trying to get my mind around it.

 

 

JR

[+SpiceWare]

Yep.

[JohnnyRockets]

Yep.

 

Got it! Thanks!

 

So, I need to really decide at some point during my "6502 learning" what system I would like to develop for...

 

Okay, well I have a lot of learning ahead of me...

 

Thanks again!

 

 

JR