Re: //e Info WANTED - Mem Maps, Bus

[dempson@atlantis.actrix.gen.nz (David Empson)]

In article <3jkf99$2so@yama.mcc.ac.uk>,
Duncan Entwisle <duncane@jumper.mcc.ac.uk> wrote:
> Mem-maps - How do I go about switching memory about - for example to access
>            the 560x200 graphics.

You probably mean 560x192 (double hi-res).  This is NOT simple to
explain.  Actually accessing the memory for the screen is easy enough,
but getting a useful display out of it is pretty hard.

If you want to delve into this in any depth, I strongly recommend
getting a book which covers the details.  For example, the Apple IIe
Technical Reference, or "Understanding the Apple IIe", or similar books.

The IIe has a lot of different ways of remapping its memory, and it
would take some time to describe them all.  A quick list:

- Main and auxiliary 48k space, with separate soft-switches for
  controlling read and write accesses.
- Main and auxiliary zero page/stack/language card space.
- Language card/ROM switching, with two 4k banks in the D000-DFFF area
  and a common 8k bank in E000-FFFF.
- Bank switching of the 80-column text screen and double hi-res
  graphics screen memory (page 1 only).
- Third-party memory expansion cards in the auxiliary slot.
- Memory expansion cards in standard slots.

> Bus      - How does BASIC communicate with the slots - I could do it
>            easily in m/c or by peeking/poking, but what about pr#n and
>            ip#n?

I don't understand what you are asking.  I assume you want to access
unspecified I/O cards from BASIC.  It would help if you could indicate
what type of cards you intend to access (e.g. disk drive interfaces,
serial I/O cards), and, if possible, the exact cards in question.  The
rules for accessing cards vary considerably depending on what type of
card it is.

-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand