Re: IBS AP17 RAM card

[Patrick Schaefer <PSchaefer@epost.de>]

Brian,

> Do you read German? I have five porly photocopied pages documenting
> the operation of the  IBS AP17.
> 
> I can try to have the pages scanned and emailed to you.

Thank you, I would really appreciate it :-)

Last week I have drawn a schematic diagram of the board, but to
completely understand the logic equations in the proms I need a
description of the soft switches.
When it is finished I can send you a copy of the schematic in exchange.

Regards
Patrick


This is PROM AP17_IBS1 (82S123):

   /RAMSEL = ! R/-W & /IOSEL & ! A16 
           + ! A15 & /IOSEL 
           + ! A1ltchd & /IOSEL & ! A2ltchd 
           + ! A14 & /IOSEL 
           + ! A12 & ! A13 & A1ltchd & R/-W & /IOSEL 
           + ! A12 & ! A13 & A1ltchd & /IOSEL & A16 
           + ! A12 & ! A13 & R/-W & /IOSEL & A2ltchd 
           + ! A12 & ! A13 & /IOSEL & A16 & A2ltchd ; 

   /DIR245 = ! R/-W ; 

   /INH = ! R/-W & ! A16 
        + ! A15 
        + ! A1ltchd & ! A2ltchd 
        + ! A14 
        + ! A12 & ! A13 & A1ltchd & R/-W 
        + ! A12 & ! A13 & A1ltchd & A16 
        + ! A12 & ! A13 & R/-W & A2ltchd 
        + ! A12 & ! A13 & A16 & A2ltchd ; 

   /OE257 = ! /IOSEL ; 

   /WE_RAM = R/-W ; 

   RA6A = A13 & A2ltchd ; 
   RA6B = A12 & A2ltchd ; 
   RA7A = A12 & A1ltchd 
        + A1ltchd & A2ltchd ; 


and this is PROM AP17_IBS2 (82S123):

 ! /RAS1 = ! A17 & ! A3ltchd & ! /RAS 
         + ! /IOSEL & ! /RAS ; 
 ! /RAS2 = /IOSEL & ! A17 & A3ltchd & ! /RAS ; 
 ! /RAS3 = /IOSEL & A17 & ! A3ltchd & ! /RAS ; 
 ! /RAS4 = /IOSEL & A17 & A3ltchd & ! /RAS ; 

 ! /CAS1 = ! A17 & ! A3ltchd & ! /CAS 
         + ! /IOSEL & ! /CAS ; 
 ! /CAS2 = /IOSEL & ! A17 & A3ltchd & ! /CAS ; 
 ! /CAS3 = /IOSEL & A17 & ! A3ltchd & ! /CAS ; 
 ! /CAS4 = /IOSEL & A17 & A3ltchd & ! /CAS ;