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From: holzer@ztivax.UUCP (Walter Holzer)
Newsgroups: comp.sys.atari.st
Subject: Mega ST with old roms - now it works
Message-ID: <657@ztivax.UUCP>
Date: 5 Apr 89 11:47:51 GMT
Reply-To: holzer@ztivax.UUCP (Walter Holzer)
Organization: Siemens AG in Munich, W-Germany
Lines: 60


Ok, here it is, the completly workaround to work with old rom's in mega st.
There was a mistake in the translation table, but now it will works.
You'll have to do the following things:
- Jumper W2 from 2-3 to 1-2
- Jumper W3 from 2-3 to 1-2
- Close Jumper W4
- Plug out chip U12 (or disable pin 12).

Have fun it's working in my mega st
-- Matthias

====================================================================
Uxx = U<socket> ! will be in ! adress
in 260/520/520+ ! MEGA ST2/4 ! 
Board <= Rev.H  !            !
----------------+------------+--------------------------
TOSyyyy.U2      ! *.U3       ! $FE0000-$FEFFFF, HiBytes
TOSyyyy.U3      ! *.U6       ! $FD0000-$FDFFFF, HiBytes
TOSyyyy.U4      ! *.U9       ! $FC0000-$FCFFFF, HiBytes
TOSyyyy.U5      ! *.U4       ! $FE0000-$FEFFFF, LoBytes
TOSyyyy.U6      ! *.U7       ! $FD0000-$FDFFFF, LoBytes
TOSyyyy.U7      ! *.U10      ! $FC0000-$FCFFFF, LoBytes

====================================================================
Schematic diagram:

                 U4 (label in Mega ST)    U3 (label in Mega ST)
                 +--------------------+   +--------------------+
                 ! was TOS.U5         !   ! was TOS.U2         !
                 ! in older ST's      !   ! in older ST's      !
                 +--------------------+   +--------------------+

                 U7 (label in Mega ST)	 U6 (label in Mega ST)
                 +--------------------+   +--------------------+
                 ! was TOS.U6         !   ! was TOS.U3         !
                 ! in older ST's      !   ! in older ST's      !
                 +--------------------+   +--------------------+

                 U10 (label in Mega ST)	 U9 (label in Mega ST)
                 +--------------------+   +--------------------+
                 ! was TOS.U7         !   ! was TOS.U4         !
                 ! in older ST's      !   ! in older ST's      !
                 +--------------------+   +--------------------+
  W4
  o
  !	+--------+	   plug out complete chip or
  !	!   U12  !  <----  disable pin 12
  o	+--------+

  1  2  3      1  2  3
  o--o  o      o--o  o
     W2	          W3
====================================================================

-- 
Walter Holzer & Matthias Dominick    Internet: holzer@ztivax.siemens.com
UUCP: holzer@ztivax.UUCP             or      : uunet!mcvax!unido!ztivax!holzer
XNS : Dominick:ZTISOF:SIEMENS        FidoNet : Matthias Dominick on 2:507/414.28
       Herman Munster said:  "I've got it! I've got it! I've got it! ..."