Date   : Thu, 03 Aug 2006 12:06:05 +0100
From   : "Steve O'Leary" <navalenigma@...>
Subject: Re: Electron cartridge interface

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> Date: Thu, 3 Aug 2006 11:42:28 +0100> From: hick.bbc@...> To: bbc-mi
cro@...> Subject: Re: [BBC-Micro] Electron cartridge interface> >
On Thu, 3 Aug 2006, Steve O'Leary wrote:> > > It's been a long time since I
've looked at this and most of the > > connections are obvious but some cou
ld benefit from a description. For > > example the ROM_OE which I would haz
ard a guess is the ROM Output Enable > > and this would go hi when the elec
tron is wanting to page in a sideways > > ROM/RAM. But this is only a guess
 ?> > It goes high on a memory access to either valid ROM socket (0,1 or 2,
3) > for the slot.> > (ROM)QA provides the low bit of the ROM socket access
ed.> > There is also a select line for ROM socket 13, it's probably A19 > "
reserved".> 
That's great it was mostly the ROM access I was interested in. I thought th
at you could only access 2 roms per slot but couldn't see how they could be
 selected, the QA solves this riddle. Are there any more connected with sid
eways ROM/RAM access that I should be aware of (besides R/!W etc.)
 
What was special about ROM socket 13 that it was mapped to the cartridge sl
ot and how did this work if you had hardware in both cartridge slots that l
ooked at the ROM 13 line ? it couldn't use both ? Or was this feature never
 implemented on this 'reserved' line.
 
Thanks for the help.
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