bjhicks@trillium.waterloo.edu (Barbara Hicks) (04/05/89)
Hello fellow netlanders, I have need of some electronic assistance. The
problem is as follows:
I need a board for an ST that will monitor the address lines and FC0-FC2 and
perform a range check for each User Data or User Instruction fetch. I would
like to have two separate ranges, one for Data and one for Instructions.
Ideally I would like to check all 24 address lines, but I would settle for
just the upper 16. If the address is out of range on either type of fetch,
a bus error will be generated. The bus error MUST occur fast enough to prevent
a data write from actually occurring. Also, I plan to grab the address lines
from the MMU and I would like to have the whole works fit under the shielding.
Oh, and last but not least, these ranges must of course be programmable via
software (like writing to $ffxxxx or some such thing). If anyone out there has
any thoughts on the matter or any thoughts as to where to find some help,
please Email me and I will summarize for the net if there is sufficient
interest.
I do not expect to find this device to be in existence and I am quite willing
to hack it all together, but I have not played around with electronics much
since high school. I don't know what wonderful chips are available these days
and I would welcome any suggestions.
Thanks much,
-- Barbara (bjhicks@trillium)
PS please don't hesitate to mail me if you have any advice as I only have this
account for another few weeks.envcanada.nwribeal@canremote.uucp (ENVCANADA NWRIBEAL) (04/07/89)
Might it not be easier to see if a 68030 CPU or a MMU of some kind could be lashed on? The features you want are handled neatly for you. I suspect it might be difficult to prevent memory writes without adding some delay and trapping on the bus and control lines, which complicate matters for general reading and screen writes. Regards, Stu Beal. --- * Via ProDoor 2.9a --- MaS Relayer v1.00.00 Message gatewayed by MaS Network Software and Consulting/HST Internet: envcanada.nwribeal@canremote.uucp UUCP: ...!tmsoft!masnet!canremote!envcanada.nwribeal
rex@otto (Rex Jolliff) (04/10/89)
In article <13050@watdragon.waterloo.edu>, bjhicks@trillium (Barbara Hicks) writes: > > ... >perform a range check for each User Data or User Instruction fetch. I would >like to have two separate ranges, one for Data and one for Instructions. >Ideally I would like to check all 24 address lines, but I would settle for >just the upper 16. ... >-- Barbara (bjhicks@trillium) I would suggest using a 68451 mounted on a daughterboard with the CPU, but I don't know what kind of conflicts you would run into between the 68451 and the atari MMU chip. I think with some careful programming and a well planned hardware interface, this could work and provide memeory protection for the ST. Rex. -- Rex Jolliff (rex@otto.lvsun.com, {convex, texsun, mirror}!otto!rex) The Sun Newspaper - |Disclaimer: The opinions and comments in Nevada's Largest Daily Morning | this article are my own and in no way Newspaper | reflect the opinions of my employers. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -