ARM R4 Computer Hardware User Manual


 
Events and Performance Monitor
ARM DDI 0363E Copyright © 2009 ARM Limited. All rights reserved. 6-11
ID013010 Non-Confidential, Unrestricted Access
Figure 6-4 FLAG Register format
Table 6-5 shows how the bit values correspond with the FLAG Register.
To access the FLAG Register, read or write CP15 with:
MRC p15, 0, <Rd>, c9, c12, 3 ; Read FLAG Register
MCR p15, 0, <Rd>, c9, c12, 3 ; Write FLAG Register
If an overflow flag is set to 1 in the FLAG register it remains set until one of the following
happens:
writing 1 to the flag bit in the FLAG Register clears the flag
the processor is reset.
The following operations do not clear the overflow flags:
disabling the overflowed counter in the CNTENC Register
disabling all counters in the PMNC Register
resetting the overflowed counter using the PMNC Register.
6.3.5 c9, Software Increment Register
The Software INCRement (SWINCR) Register increments the count of a Performance Monitor
Count Register.
The SWINCR Register is:
A write-only register that Reads-As-Zero
Always accessible in Privileged mode. The USEREN Register determine accessibility in
User mode, see c9, User Enable Register on page 6-15.
Caution
You must only use the SWINCR Register to increment performance monitor count registers
when the counter event is set to
0x00
, software count, in the Event Select Register, see c9, Event
Selection Register on page 6-13.
C
31 3210
Reserved
P2
P1
P0
Performance monitor counters
overflow flags
Cycle count overflow
Table 6-5 Overflow Flag Status Register bit functions
Bits Field Function
[31] Cycle counter overflow Cycle counter overflow flag:
0 = disable
1 = enable.
[30:3] Reserved UNP on reads, SBZP on writes
[2] P2 Counter 2 overflow flag
[1] P1 Counter 1 overflow flag
[0] P0 Counter 0 overflow flag