Programmer’s Model
2-16 Copyright © 2001-2003 ARM Limited. All rights reserved. ARM DDI0198D
Effects of the Control Register on TCM interface
The M bit of the Control Register, when combined with the En bit in the respective TCM
region register c9, directly affects the TCM interface behavior, as shown in Table 2-13.
Table 2-13 Effects of Control Register on TCM interface
TCM MMU Cache Behavior
Instruction
TCM disabled
Disabled ICache
disabled
All instruction fetches are from the external memory (AHB).
Instruction
TCM enabled
Disabled ICache
disabled
All instruction fetches are from the TCM interface, or from external memory
(AHB), depending on the setting of the base address in the instruction TCM
region register. No protection checks are made. All addresses are flat mapped.
That is, VA = MVA= PA.
Instruction
TCM enabled
Disabled ICache
enabled
All instruction fetches are from the TCM interface, or from the ICache,
depending on the setting of the base address in the Instruction TCM region
register. No protection checks are made. All addresses are flat mapped. That is,
VA = M VA = PA .
Instruction
TCM enabled
Enabled ICache
enabled
All instruction fetches are from the TCM interface, or from the ICache/AHB
interface, depending on the setting of the base address in the Instruction TCM
region register. Protection checks are made. All addresses are remapped from
VA to PA, depending on the page entry. That is, the VA is translated to an MVA,
and the MVA is remapped to a PA.
Data TCM
disabled
Disabled DCache
disabled
All data accesses are to external memory (AHB).
Data TCM
enabled
Disabled DCache
disabled
All data accesses are to the TCM interface, or to the external memory, depending
on the setting of the base address in the data TCM region register. No protection
checks are made. All addresses are flat mapped. That is, VA = MVA= PA.
Data TCM
enabled
Disabled DCache
enabled
All data accesses are to the TCM interface or to external memory, depending on
the setting of the base address in the data TCM region register. All addresses are
flat mapped. That is, VA =MVA = PA.
Data TCM
enabled
Enabled DCache
enabled
All data accesses are either from the TCM interface, or from the DCache/AHB
interface, depending on the setting of the base address in the data TCM region
register. Protection checks are made. All addresses are remapped from VA to PA,
depending on the page entry. That is the VA is translated to an MVA, and the
MVA is remapped to a PA.
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