ARM Cortex-R4 - Memory Types and L1 Memory System Behavior

Level One Memory System
ARM DDI 0363G Copyright © 2006-2011 ARM Limited. All rights reserved. 8-35
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8.7 Memory types and L1 memory system behavior
The behavior of the L1 memory system depends on the type attribute of the memory that is being
accessed:
• Only Normal, Non-shared memory can be cached in the RAMs.
• The store buffer can merge any stores to Normal memory. See Store buffer on page 8-18
for more information.
• Only Normal memory is considered restartable, that is, a multi-word transfer can be
abandoned part way through because of an interrupt, to be restarted after the interrupt is
handled. See Interrupts on page 3-16 for more information about interrupt behavior.
• Only the internal exclusive monitor is used for exclusive accesses to Non-shared memory.
Exclusive accesses to shared memory are checked using the internal monitor and also, if
necessary, any external monitor, using the L2 memory interface.
• Accesses resulting from
SWP and SWPB instructions to Normal, non-shared memory are not
marked as locked when performed using the L2 memory interface.
Table 8-17 summarizes the processor memory types and associated behavior.
Table 8-17 Memory types and associated behavior
Memory type Can be cached Merging Restartable
Internal
exclusives
Locked
swaps
Normal Shared No Yes Yes Partially Yes
Non-shared Yes Yes Yes Yes No
Device Shared No No No Partially Yes
Non-shared No No No Yes Yes
Strongly-ordered Shared No No No Partially Yes