Cortex-A8 Technical Reference Manual - ARM Information Center

EN b
3.2.49 c9, Event Selection Register
Table 3-94 shows the results of attempted access for each mode.
To access the CCNT Register, read or write CP15 with:
MRC p15, 0, , c9, c13, 0 ; Read CCNT Register
MCR p15, 0, , c9, c13, 0 ; Write CCNT Register
System Control Coprocessor
Table 3-94 Results of access to the Cycle Count Register a
Secure privileged Nonsecure privileged Secure User Nonsecure User
Read Write Read Write Read Write Read Write
0 Data Data Data Data Undefined Undefined Undefined Undefined
1 Data Data Data Data Data Data Data Data
a. An entry of Undefined in the table means that the access gives an Undefined Instruction exception when the coprocessor
instruction is executed.
b. The EN bit in c9, User Enable Register on page 3-89 enables User mode access of the Performance Monitor Registers.
The CCNT Register must be disabled before software can write to it. Any attempt by software
to write to this register when enabled is Unpredictable.
The purpose of the Event SELection (EVTSEL) Register is to select the events that you want a
Performance Monitor Count Register to count.
The EVTSEL Register is:
• a read/write register common to Secure and Nonsecure states
• accessible as determined by c9, User Enable Register on page 3-89.
Figure 3-44 shows the bit arrangement of the EVTSEL Register.
31 8 7
0
Reserved SEL
Figure 3-44 Event Selection Register format
Table 3-95 shows how the bit values correspond with the EVTSEL Register functions.
Bits Field Function
[31:8] - Reserved. RAZ, SBZP
Table 3-95 Event Selection Register bit functions
[7:0] SEL Specifies the event selected as shown in Table 3-97 on page 3-85
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