Addressing 2GS slots with Orca Pascal?

[Yves McDonald <""yves.mcdonald\"@NO SPAM sympatico.ca>]

Hello Apple 2 fans,

I'm an experienced Apple ][+, //e programmer but a newbie when it comes 
to Apple 2GS 16-bit mode.  I whish to experiment with a sprite card 
based on TI's TMS9918A chip.  I'd like to use Orca PASCAL for this 
instead of fiddling with PEEKs and POKES and their negative decimal 
addresses and data or using assembler which is tedious to use for a 
first try.  I'll use assembler later on to write a more efficient device 
driver.  Anyway, here's my question: is there a PASCAL programming trick 
to access memory space dedicated to slot 1-7?  On the same line of 
thought,  are there online reference on GS hardware architecture?  I 
have the Toolbox reference books vol. 1 and 2 but I miss the rest of 
official Apple 2gs book collection.

Thanks,

Yves