How can you write and read the 1088 kb Ram in the Altirra (800xl)?

funkheld · November 7, 2016

How can you write and read the 1088 kb ext Ram in the Altirra (800xl) with Action! ?

thank you.

greeting

Edited November 7, 2016 by funkheld

Rybags · November 8, 2016

I'm fairly sure this came up recently in another thread.

With high-level languages you have less control over where the executing code is. The important thing is that the code performing bank switches doesn't reside within the region of $4000-$7FFF since that's the window for banked memory with the 130XE and virtually all of the memory expansions for XL and later.

That said, you need to then selectively save and change bits of the PIA PORTB register to change the active memory bank. Then restore back to default if any data or code that lives in the main memory for that area is needed.

In a high level language it's probably easiest to do record oriented access to expanded Ram, ie deal with chunks of 128, 256 or more bytes at a time.