Date   : Mon, 08 Jan 1996 20:24:44 GMT0BST
From   : "Tom Seddon" <T.W.Seddon@...>
Subject: VIA queries

I know this will be fairly straightforward stuff for you but I'm 
still only getting started on the second version of my emulator (my 
hard disk died when installing Windows 95). My questions concern the 
system VIA. I'm sorry about the length of this e-mail.
(I haven't got my AUG with me as I write so some of the names or
addresses may be incorrect.)

1. Looking at the source for Xbeeb it only seems to use the 
non-handshaking port A (at &FE4F) as keyboard input/output. Does the 
handshaking port A (&FE41, I think) work in the same way as far as 
the keyboard goes? I'm not doing the user VIA (apart from timers) yet 
so the exact difference between handshaking and no handshaking 
doesn't really bother me.

2. To get the keyboard working, is it sufficient to sort out only
port A, DDRA, the addressable latch and the CB1 (or is it CB2) IRQ?
Or will the OS need other bits as well? I seem to remember someone 
saying it uses the timers for the keyboard repeat, but will it work 
without them (I just want to get the basic INKEY keyboard scan 
facility before I get started on anything else).

And also, what sort of speeds are people getting on their emulators? 
I'm leaving major optimisations until I've got the thing working, but 
I'd like to get a general idea of the sort of speed I should be 
aiming for.

Thanks in advance for any help,

--Tom
     .                 ** Tom Seddon **                 .
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