Level 2 Memory System
ARM DDI 0500D
Copyright © 2013-2014 ARM. All rights reserved.
7-9
ID021414
Non-Confidential
•
INCR 1 8-bit, 16-bit, 32-bit, 64-bit, and 128-bit for exclusive read transfers.
For Device transactions:
•
INCR N (N:1, 2, or 4) 128-bit read transfers.
•
INCR N (N:1, 2, or 4) 128-bit write transfers.
•
INCR 1 8-bit, 16-bit, 32-bit, 64-bit, and 128-bit read transfers.
•
INCR 1 8-bit, 16-bit, 32-bit, 64-bit, and 128-bit write transfers.
•
INCR 1 8-bit, 16-bit, 32-bit, 64-bit, and 128-bit exclusive read transfers.
•
INCR 1 8-bit, 16-bit, 32-bit, 64-bit, and 128-bit exclusive write transfers.
For translation table walk transactions INCR 1 32-bit, and 64-bit read transfers.
The following points apply to AXI transactions:
•
WRAP bursts are only 128-bit.
•
INCR 1 can be any size for read or write.
•
INCR burst, more than one transfer, are only 128-bit.
•
No transaction is marked as FIXED.
•
Write transfers with none, some, or all byte strobes LOW can occur.
Table 7-8
shows the ACE transactions that can be generated, and some typical operations that
might cause the transactions to be generated. This is not an exhaustive list of ways to generate
each type of transaction, because there are many possibilities.
Table 7-8 ACE transactions
Transaction
Operation
ReadNoSnoop
Non-cacheable loads or instruction fetches. Linefills of non-shareable cache lines into L1 or L2.
ReadOnce
Cacheable loads that are not allocating into the cache, or cacheable instruction fetches when there is no L2
cache.
ReadClean Not
used.
ReadNotSharedDirty Not
used.
ReadShared
L1 Data linefills started by a load instruction, or L2 linefills started by an instruction fetch.
ReadUnique
L1 Data linefills started by a store instruction.
CleanUnique
Store instructions that hit in the cache but the line is not in a unique coherence state. Store instructions that
are not allocating into the L1 or L2 caches, for example when streaming writes.
MakeUnique
Store instructions of a full cache line of data, that miss in the caches, and are allocating into the L2 cache.
CleanShared
Cache maintenance instructions.
CleanInvalid
Cache maintenance instructions.
MakeInvalid Cache
maintenance instructions.
DVM
TLB and instruction cache maintenance instructions.
DVM complete
DVM sync snoops received from the interconnect.
Barriers
DMB and DSB instructions. DVM sync snoops received from the interconnect.
WriteNoSnoop
Non-cacheable store instructions. Evictions of non-shareable cache lines from L1 and L2.
WriteUnique
Not used.
WriteLineUnique Not
used.