Instructions for the 384kb-sRAM-expansion

The sRAM-expansion has a similar function as the EPROM-expansion, so it uses the same
register at adress $fd17, but more bits:

Bit 0/1  Select one of 4 sRAM-areas with 96kb (each area consists of the
         banks 5, a and f)
         standard (after power on) is both bits on "1", this means standard
         area is 3, use this area first for your programs.
Bit 4    1: no writeaccess to the sRAM in bank 5
         0: write to sRAM in bank 5 from $4000-$bfff possible (depends on
            writeprotect)
Bit 5    1: no writeaccess to the sRAM in bank a
         0: write to sRAM in bank a from $4000-$bfff possible (depends on
            writeprotect)
Bit 6    1: no writeaccess to the sRAM in bank f
         0: write to sRAM in bank f from $4000-$bfff possible (depends on
            writeprotect)
Bit 7    1: external EPROMs (expansionport, bank a, f) disabled
         0: external EPROMs (expansionport, bank a, f) enabled, sRAMs on
            bank a, f disabled

Note: You can't read the sRAMs from $4000-$bfff, it's only access for write! If you read this
adress you get the data from plus/4-system-RAM, this can differ from the sRAM-value but you write in both RAMs. So
it's easy to write a complete burnfile (located $4000-$bfff) without conflict with the I/O- and
TED-area.
The RAM-adress $ff3d (or $bf3d) is reserved for test-conditions (check for write-protect).
Don't use it for code or datas. My "Modulgenerator" only use the area from $8000-$fbff
($4000-$bbff) and area for reset-vector.

Write-Protect-Switch:
On: Left position (no writing to sRAM possible)
Off: Right position

The Lithium-battery CR2032 is enough for over 2 years. But it exists some expansions from
me with a NiCd-accumulator.
