Newsgroups: comp.sys.transputer
From: hgs@allegra.att.com (Henning G. Schulzrinne)
Subject: T225 memory map
Organization: AT&T Bell Laboratories, Murray Hill, NJ
Date: Fri, 14 Jan 1994 21:23:46 GMT
Message-ID: <1994Jan14.212346.21253@allegra.att.com>

I'm trying to use a T225 as a network interface device, with a
32 kB dual-port RAM as the interface to the system. I'm a bit confused
by the memory map in the databook (the transputer must be the only
microprocessor that has "negative" memory addresses..). I want
to load as much of the code into the 4k internal RAM and not
overlap the external (dual-port) RAM. If the external RAM is wired
in standard fashion (i.e., with address bit 15 unconnected), how
do I tell the loader/linker to put the code into internal RAM (as
much as possible) and not to write over the mirrored part of the
external RAM (since the external RAM will appear twice)? Is this
scenario feasible?

Is the following memory map correct:
                         external  external
                         (hidden)  mirrored
    external             internal
   |---------------------|------|-----------|
   0                    0x8000  0x9000     0xffff

Thanks.

Henning Schulzrinne

