System Control
ARM DDI 0388I
Copyright © 2008-2012 ARM. All rights reserved.
4-39
ID073015
Non-Confidential
4.3.20
Preload Engine Parameters Control Register
The PLEPCR characteristics are:
Purpose
Contains PLE control parameters, available only in Privilege modes, to
limit the issuing rate and transfer size of the PLE.
Usage constraints
The PLEPCR is:
•
read/write register
•
only accessible in privileged mode
•
common to Secure and Non-secure states
•
NSACR.PLE controls Non-secure accesses.
Configurations
Only available in configurations where the Preload Engine is present,
otherwise an Undefined Instruction exception is taken.
Attributes
.
shows the PLEPCR bit assignments.
Figure 4-19 PLEPCR bit assignments
shows the PLEPCR bit assignments.
To access the PLEPCR, read or write the CP15 register with:
31
0
PLE wait states
RAZ
30 29
16 15
8 7
Block size mask
Block number mask
Table 4-46 PLEPCR bit assignments
Bits
Name
Function
[31:30]
-
RAZ.
[29:16]
Block size mask
Permits Privilege modes to limit the maximum block size for PLE transfers.
The transferred block size is:
(Block size) & (Block size mask).
For example, a block size mask of 14’b11111111111111 authorizes the transfer of block sizes with
the maximum value of 16k * 4 bytes. A block size mask of 14’b00000000000000 limits block sizes
to 1 * 4 bytes.
[15:8]
Block number mask
Permits Privilege modes to limit the maximum number of blocks for a single PLE transfer.
The transferred block number is:
(Block number) & (Block number mask).
For example, a block number mask of 8’b11111111 authorizes the transfer of a maximum possible
number of 256 blocks. A block number mask of 8’b00000000 limits the transfer to only one block
of data.
[7:0]
PLE wait states
Permit Privilege modes to limit the issuing rate of PLD requests performed by the PLE engine to
prevent saturation of the external memory bandwidth.
PLE wait states specifies the number of cycles inserted between two PLD requests performed by the
PLE engine.
When PLE wait states is 8’b11111111, the PLE engine can issue one PLD request, a cache line, every
256 cycles.
When PLE wait states is 8’b000000000, the PLE engine can issue one PLD request every cycle.