Virtual Memory
Space
Physical Memory
Space
MMU
V
irtual
Addresses
Physical
Addresses
Translation Look-aside
Buffer
(TLB)
Table Walking Logic
Translation Tables
Preliminary
System MMU
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The System MMU is dedicated to C674x™ MDMA and other requestors. The system MMU configuration
is done through MMU_CFG register (refer Control Module chapter). The MMU_CFG register is used to
optionally route certain requestors through the System MMU. The C674x™ MDMA port accesses will
always be routed through the System MMU so no configuration bit is instantiated for C674x™.
1.4.3 MMU Functional Description
1.4.3.1
MMU Block Diagram
The MMU manages the virtual to physical address translation for external addresses, as well as
endianness conversion. The MMU can be programmed through the L3 interconnect.
Figure 1-12. MMU Block Diagram
Each table entry describes the translation of one contiguous memory region. For a description of the
structure of these tables, see Translation Tables.
Two major functional units exist in the MMU to provide address translation automatically based on the
table entries:
•
The table walker automatically retrieves the correct translation table entry for a requested translation. If
two-level translation is used (for the translation of small memory pages), the table walker also
automatically reads the required second-level translation table entry. The two-level translation is
described later in the chapter.
•
The translation look-aside buffer (TLB) stores recently used translation entries, acting like a cache of
the translation table.
1.4.3.1.1 MMU Address Translation Process
Whenever an address translation is requested (that is, for every access with the MMU enabled), the MMU
first checks whether the translation is contained in the TLB, which acts like a cache storing recent
translations. The TLB can also be programmed manually to ensure that time-critical data can be translated
without delay.
If the requested translation is not in the TLB, the table-walking logic retrieves this translation from the
translation table(s), and then updates the TLB. The address translation is then performed.
summarizes the process.
118
Chip Level Resources
SPRUGX9 – 15 April 2011
© 2011, Texas Instruments Incorporated
Содержание TMS320C6A816 Series
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