ARM Cortex R4F - Manual (Page 173)

Events and Performance Monitor
ARM DDI 0363E Copyright © 2009 ARM Limited. All rights reserved. 6-9
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Figure 6-2 CNTENS Register format
Table 6-3 shows how the bit values correspond with the CNTENS Register.
To access the CNTENS Register, read or write CP15 with:
MRC p15, 0, <Rd>, c9, c12, 1 ; Read CNTENS Register
MCR p15, 0, <Rd>, c9, c12, 1 ; Write CNTENS Register
The CNTENS Register retains its value when the enable bit of the PMNC is clear, even though
its settings are ignored.
6.3.3 c9, Count Enable Clear Register
The CouNT ENable Clear (CNTENC) Register disables any of the Performance Monitor Count
Registers.
When reading this register, any enable that reads as 0 indicates the corresponding counter is
disabled. Any enable that reads as 1 indicates the corresponding counter is enabled.
When writing this register, any enable written with a value of 0 is ignored, that is, not updated.
Any enable written with a value of 1 clears the counter enable.
The CNTENC Register is:
• A read/write register
• Always accessible in Privileged mode. The User Enable Register determines accessibility
in User mode, see c9, User Enable Register on page 6-15.
Figure 6-3 on page 6-10 shows the bit arrangement for the CNTENC Register.
C
31 3 2 1 0
Reserved
P2
P1
P0
Performance monitor
counter enables
Cycle count enable
Table 6-3 CNTENS Register bit functions
Bits Field Function
[31] C Cycle counter enable set:
0 = disable
1 = enable.
[30:3] Reserved UNP on reads, SBZP on writes
[2] P2 Counter 2 enable
[1] P1 Counter 1 enable
[0] P0 Counter 0 enable