Level 2 Memory System
ARM DDI 0500D
Copyright © 2013-2014 ARM. All rights reserved.
7-13
ID021414
Non-Confidential
7.4
CHI master interface
This section describes the properties of the CHI master interface. The CHI interface to the
system can be clocked at integer ratios of the
CLKIN
frequency.
7.4.1
Memory interface attributes
Table 7-11
shows the CHI master interface attributes for the Cortex-A53 processor. The table
lists the maximum possible values for the read and write issuing capabilities if the processor
includes four cores.
Table 7-11 CHI master interface attributes
Attribute
Value
a
Comments
Write issuing
capability
Configuration
dependent
The maximum number of writes varies, depending on the configuration of the processor:
•
The number of cores.
•
The presence of the L2 cache.
If no L2 cache is configured:
One core
5 outstanding writes.
2-4 cores
8 outstanding writes.
If an L2 cache is configured:
One core
7 outstanding writes.
2-4 cores
10 outstanding write.
A Cortex-A53 processor configured with four cores, with L2 cache, can issue 10 outstanding
transactions. A Cortex-A53 processor configured with one core, without L2 cache, can issue
five outstanding transactions.
All outstanding transactions use a unique ID.
Read issuing
capability
8n + 4m + 1
8 for each core in the cluster including up to:
•
8 data linefills.
•
4 Non-cacheable or Device data reads.
•
1 Non-cacheable TLB page-walk read.
•
3 instruction linefills.
•
5 coherency operations.
•
1 barrier operation.
•
8 DVM messages.
If an ACP is configured, up to 4 ACP linefill requests can be generated. 1 barrier operation is
generated from the cluster.
Exclusive thread
capability
n
Each core can have 1 exclusive access sequence in progress.
Transaction ID
width
8
The ID encodes the source of the memory transaction. See
Table 7-6 on page 7-7
and
Table 7-7 on page 7-8
.
Transaction ID
capability
8n + 4m + w + 1
8 for each core in the cluster in addition to:
•
4 for the ACP interface.
•
1 for barriers.
•
6 to 11 writes, depending on the write issuing capability.
Unlike an AMBA 4 ACE configured Cortex-A53 processor, there is never any ID reuse,
regardless of the memory type.
a. n is the number of cores.
m is the ACP interface.
w is the write issuing capability plus one.