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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors—Intel XScale
®
Processor
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
Developer’s Manual
August 2006
158
Order Number: 306262-004US
3.7.2
Register Description
3.7.2.1
Clock Counter (CCNT)
The format of CCNT is shown in
. The clock counter is reset to ‘0’ by setting bit
2 in the Performance Monitor Control Register (PMNC) or can be set to a predetermined
value by directly writing to it. It counts core clock cycles. When CCNT reaches its
maximum value 0xFFFF,FFFF, the next clock cycle will cause it to roll over to zero and
set the overflow flag (bit 0) in FLAG. An interrupt request will occur if it is enabled via
bit 0 in INTEN.
3.7.2.2
Performance Count Registers
There are four 32-bit event counters; their format is shown in
. The event
counters are reset to ‘0’ by setting bit 1 in the PMNC register or can be set to a
predetermined value by directly writing to them. When an event counter reaches its
maximum value 0xFFFF,FFFF, the next event it needs to count will cause it to roll over
to zero and set its corresponding overflow flag (bit 1,2,3 or 4) in FLAG. An interrupt
request will be generated if its corresponding interrupt enable (bit 1,2,3 or 4) is set in
INTEN.
Table 56.
Register Legend
Attribute
Legend
Attribute
Legend
RV
Reserved
RC
Read Clear
PR
Preserved
RO
Read Only
RS
Read/Set
WO
Write Only
RW
Read/Write
NA
Not Accessible
RW1C
Normal Read
Write ‘1’ to clear
RW1S
Normal Read
Write ‘1’ to set
Table 57.
Clock Count Register (CCNT)
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
Clock Counter
reset value: unpredictable
Bits
Access
Description
31:0
Read / Write
32-bit clock counter - Reset to ‘0’ by PMNC register.
When the clock counter reaches its maximum value
0xFFFF,FFFF, the next cycle will cause it to roll over to
zero and generate an interrupt request if enabled.
Table 58.
Performance Monitor Count Register (PMN0 - PMN3)
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
Event Counter
reset value: unpredictable
Bits
Access
Description
31:0
Read / Write
32-bit event counter - Reset to ‘0’ by PMNC register.
When an event counter reaches its maximum value
0xFFFF,FFFF, the next event it needs to count will cause it
to roll over to zero and generate an interrupt request if
enabled.