41CL User Manual
© 2019, Systemyde International Corporation
22
MMU Functions
The MMU Functions allow the user to initialize, enable, disable, and test the status of the
MMU.
MMUCLR
Executing
MMUCLR
(
MMU Clear
) clears the contents of all of the regular MMU regis-
ters (for Pages 4-F) in memory, by writing 0x0000 to these registers.
MMUCLR
will
result in all pages (except for the Operating System, Extended Functions, Time Functions
and
41CL Extra Functions
) being fetched from the Ports rather than fetched from internal
memory.
To prevent unpredictable results, this function should only be executed while the
MMU is disabled.
MMUDIS
Executing
MMUDIS
(
MMU Disable
) clears the global MMU enable bit inside the NEWT
microprocessor. This automatically reassigns the
41CL Extra Functions
to Page 7, but
only after the code returns to executing in one of the Operating System pages. This
delayed switch allows the function to complete normally and return to the Operating Sys-
tem. This function does not affect the MMU register contents in memory.
MMUEN
Executing
MMUEN
(
MMU Enable
) sets the global MMU enable bit inside the NEWT
microprocessor. This automatically disables mapping of the
41CL Extra Functions
to
Page 7, but only after the code returns to executing in one of the Operating System pages.
This delayed switch allows the function to complete normally and return to the Operating
System. The
41CL Extra Functions
must have been assigned to some other page prior to
executing
MMUEN
, or the
41CL Extra Functions
will no longer be available to the user.