MC68030 Datasheet, PDF (323/602 Pages) Motorola, Inc – ENHANCED 32-BIT MICROPROCESSOR

Memory Management Unit
(UNABLE TO LOCATE ART)
Figure 9-28. Limit Check Procedure Flowchart
9.5.5 Protection
M68000 Family processors provide an indication of the context in which they are operating
on a cycle-by-cycle basis by means of the function code signals. These signals identify
accesses to the user program space, the user data space, the supervisor program space,
and the supervisor data space. The function code signals can be used for protection
mechanisms by setting the function code lookup (FCL) bit in the translation control (TC)
register.
The MC68030 MMU provides the capability for separate translation trees for supervisor and
user spaces to be used. When the supervisor root pointer enable bit (SRE) in the TC register
is set, the root pointer register for the supervisor space translation tree is selected for
supervisor program or data accesses.
The translation table trees contain both mapping and protection information. Each table and
page descriptor includes a write-protect (WP) bit, which can be set to provide write
protection at any level. Each long-format table and page descriptor also contains a
supervisor-only (S) bit, which can limit access to programs operating at the supervisor
privilege level.
MOTOROLA
MC68030 USER’S MANUAL
9-35