MC68030 Datasheet, PDF (338/602 Pages) Motorola, Inc – ENHANCED 32-BIT MICROPROCESSOR

Memory Management Unit
The bits in the MMUSR have different meanings for the two kinds of PTEST instructions, as
shown in Table 9-3.
Table 9-3. MMUSR Bit Definitions
MMUSR Bit
Bus Error (B)
Limit (L)
Supervisor Violation (S)
Write Protected (W)
Invalid (I)
Modified (M)
Transparent (T)
Number of Levels (N)
PTEST, Level 0
PTEST, Level 1-7
This bit is set if the bus error bit is This bit is set if a bus error is
set in the ATC entry for the
encountered during the table
specified logical address.
search for the PTEST instruction.
This bit is cleared.
This bit is set if an index exceeds a
limit during the table search
This bit is cleared
This bit is set if the S bit of a long (S)
format table descriptor or long
format page descriptor
encountered during the search is
set, and the FC2 bit of the function
code specified by the PTEST
instruction is not equal to one. The
S bit is undefined if the I bit is set.
This bit is set if the WP bit of the This bit is set if a descriptor or page
ATC entry is set. It is undefined if descriptor is encountered with the
the I bit is set
WP bit set during the table search.
The W bit is undefined if the I bit is
set.
This bit indicates an invalid
This bit indicates an invalid
translation. The I bit is set if the translation. The I bit is set if the DT
translation for the specified logical field of a table or a page descriptor
address is not resident in the ATC encountered during the serach is
or if the B bit of the corresponding set to invalid or if either the B or L
ATC entry is set.
bits of the MMUSR are set during
the table search.
This bit is set if the ATC entry
This bit is set if the page descriptor
corresponding to the specified
for the specified address has the
address has the modified bit set. It modified bit set. It is undefined if I is
is undefined if the I bit is set.
set.
This bit is set if a match occurred in This bit is set to zero.
either (or both) of the transparent
translation registers (TT0 or TT1). If
the T bit is set, all remaining
MMUSR bits are undefined.
This 3-bit field is cleared to zero. This 3-bit field contains the actual
number of tables accessed during
the search.
9-50
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