MC68030 Datasheet, PDF (324/602 Pages) Motorola, Inc – ENHANCED 32-BIT MICROPROCESSOR

Memory Management Unit
(UNABLE TO LOCATE ART)
Figure 9-29. Detailed Flowchart of Descriptor Fetch Operation
The protection mechanisms can be used individually or in any combination to protect:
• Supervisor program and data spaces from access by user programs.
• User program and data spaces from access by other user programs or supervisor pro-
grams (except with the MOVES instruction).
• Supervisor and user program spaces from write accesses (except by the supervisor us-
ing the MOVES instruction).
• One or more pages of memory from write accesses.
9.5.5.1 FUNCTION CODE LOOKUP. One way of protecting supervisor and user spaces
from unauthorized access is to set the FCL bit in the TC register. This effectively segments
the logical address space into a supervisor program space, a supervisor data space, a user
program space, and a user data space, as shown in Figure 9-30. Each task has an address
translation tree with unique mappings for the logical addresses in its user spaces. The
translation tables for mapping the supervisor spaces can be copied into each task's
translation tree. Figure 9-31 shows a translation tree using function code lookup, and Figure
9-32 shows translation trees for two tasks that share common supervisor spaces.
(UNABLE TO LOCATE ART)
Figure 9-30. Logical Address Map Using Function Code Lookup
9-36
MC68030 USER’S MANUAL
MOTOROLA