MC68030RC25C Freescale Semiconductor, MC68030RC25C Datasheet - Page 335

• Manufacturer Part Number: MC68030RC25C
• Description: IC MPU 32BIT ENHANCED 128-PGA
• Manufacturer: Freescale Semiconductor

Specifications of MC68030RC25C

• Processor Type: M680x0 32-Bit
• Speed: 25MHz
• Voltage: 5V
• Mounting Type: Surface Mount
• Package / Case: 128-PGA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -

9
9.5.3.2 INDIRECTION.
9-34
with the bits used in the search set to zero.
Although the early termination page descriptor creates a contiguous logical-
to-physical mapping without having to maintain individual descriptors in the
translation tree for each page that is a member of the contiguous region, the
ATC contains one entry for each page mapped. These entries are created
table with a portion of the logical address space translated as a contiguous
translation tree including the root pointer level. Setting the DT field of a root
the table address field of the root pointer.
allows multiple tasks to share a physical page while maintaining only a single
set of history information for the page (i.e., the " m o d i f i e d " indication is
When the MC68030 has completed a normal table search (has exhausted all
of the last entry fetched from the translation tables. If the DT field contains
a "valid long" ($2) or "valid short" ($3) encoding, this indicates that the
address contained in the highest order 30 bits of the table address field of
the descriptor is a pointer to the page descriptor that is to be used to map
the logical address. The processor then fetches the page descriptor of the
When a search is made for a logical address to which an early termination
address field in the descriptor plus an offset. The offset is the logical address
crossed in the contiguous region. Figure 9-21 shows an example translation
block.
Note that the DT field can be set to page descr!ptor at any level of the
pointer to page descriptor creates a direct mapping from the logical to the
physical address space with a constant offset as determined by the value in
page table with a pointer to an alternate entry. The indirection capability
maintained only in the single descriptor). The indirection capability also al-
lows the page frame to appear at arbitrarily different addresses in the logical
address spaces of each task.
Using the indirection capability, single entries or entire tables can be shared
between multiple tasks. Figure 9-22 shows two tasks sharing a page using
indirect descriptors.
index fields of the logical page address), it examines the descriptor-type field
indicated format from this address and uses the page address field of the
page descriptor as the physical mapping for the logical address.
page descriptor applies, the MC68030 creates an entry in the ATC for the
logical address; the physical address in the ATC entry is the sum of the page
internally each time a page boundary (as determined by the page size) is
The MC68030 provides the ability to replace an entry in a
MC68030 USER'S MANUAL
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