S P E C T R U M    

                       [  S O F T R O M  ]

                       ===================

The SOFT-ROM is a 16K RAM board which uses the same memory space
as the Spectrums internal ROM. Once loaded with the Sinclair
operating system ( or even your own! ) the Spectrum's ROM is
disabled leaving you with a 64K RAM computer.

The uses to which a SOFT-ROM can be put are only limited by the
skill and ingenuity of the programmer. Some of them may include
the following :-
Change the RESET code at 0 to give an ESCAPE Function
Use the non-maskable interupt (NMI) to stop programs.
Alter the SAVE/LOAD routines for other baud rates.
Addition of extra commands     e.g. Hex notation.
etc. etc.

Switching between the Sinclair ROM and the SOFT-ROM RAM is by
switch on the unit labelled NORM/SOFT.

To protect the software held in SOFT-ROM a WRITE DISABLE
is included. This has been found necessary as parts
Sinclair operating swstem overwrites itself!


Other Features included on the unit are RESET and NMI switches
which have the following functions :-

RESET
On delivery this switch is set up to take the RESET line
to the Z8O low for as long as the switch is in the RESET
position. To avoid memory corruption ( see notes an
Dynamic RAMs ) the small red link on the underside of
the SOFT-ROM may be removed and the 1uF capacitor (C27)
internal to the Spectrum also removed to allow a short
pulse RESET of approximately 12 uS to be used.

NMI
This switch will not generate a non-maskable interrupt
with the SOFT-ROM in the NORM mode as this would serve
no useful purpose. When in SOFT mode, activation will
cause an interrupt to be serviced.

Also, there is the facility to generate an NMI, at the
instance of change over from NORM to SOFT, by switching
to NMI while in NORM mode, when the switch over, is made
there will be an automatic jump to 66h.

The SOFT-ROM will operate with Interface 1 but as it uses the
ROMCS  line to disable the internal Spectrum ROM, the SHADOW ROM
is also disabled. Therefore, no Microdrive commands etc. can be
used when in SOFT mode. Interface 1 will Function as normal when
the SOFT-ROM is switched to NORM. There is a hardware fix to
this problem requiring a small modification to Interface 1
(details available).

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