41CL Calculator Manual
© 2019 Systemyde International Corporation
44
MAPEN
(passphrase in ALPHA register)
Executing
MAPEN
(
Enable Special MMU Mapping
) sets the special MMU enable bit
inside the NEWT microprocessor, but only if the correct passphrase (
NEW OS
) is
present in the ALPHA register.
An incorrect passphrase will result in a
PASS ERR
message.
This function automatically enables mapping of the Operating System pages, but only if
the MMU is globally enabled. The
MAPEN
and
MMUEN
commands may be issued in
either order. All of the normal MMU entries must be valid before the
MMUEN
command
is issued, and all of the special MMU entries (Pages 0-3 and 5) must be valid before the
MAPEN
command is issued.
The
MAPEN
function uses the normal 41C call/return convention, which means that the
function will return through address 0x00F0. Any modified Operating System must take
this into account. If necessary, this function can be patched to return through address
0x0000. Contact the factory for the details of this patch.
