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The Performance Control Register in SPARC64 V is illustrated in
described in
0
OVF
63
48
47
32
FIGURE 5-1
Bit Description
PCR
TABLE 5-2
Bit
Field
47:32
OVF
26
OVRO
24:22
NC
20:18
SC
16:11
SU
9:4
SL
3
ULRO
2
UT
1
ST
Release 1.0, 1 July 2002
.
TABLE 5-2
NC
0
OVRO
0
31
27
26
25
24
22
SPARC64 V Performance Control Register (PCR) (ASR 16)
Description
Overflow Clear/Set/Status. Used to read counter overflow status (via RDPCR) and clear
or set counter overflow status bits (via WRPCR). PCR.OVF is a SPARC64 V-specific field
(impl. dep. #207).
The following figure depicts the bit layout of SPARC64 V OVF field for four counter
pairs. Counter status bits are cleared on write of 0 to the appropriate OVF bit.
15
Overflow read-only. Write-only/read-as-zero field specifying PCR.OVF update behavior
for WRPCR.PCR. The OVRO field is implementation -dependent (impl. dep. #207).
WRPCR.PCR with PCR.OVRO = 1 inhibits updating of PCR.OVF for the current write
only. The intention of PCR.OVRO is to write PCR while preserving current PCR.OVF
value. PCR.OVF is maintained internally by hardware, so a subsequent RDPCR.PCR
returns accurate overflow status at the time.
Number of counter pairs. Three-bit, read-only field specifying the number of counter
pairs, encoded as 0–7 for 1–8 counter pairs (impl. dep. #207).
For SPARC64 V, the hardcoded value of NC is 3 (indicating presence of 4 counter pairs).
Select PIC. In SPARC64 V, three-bit field specifying which counter pair is currently
selected as PIC (ASR 17) and which SU/SL values are visible to software. On write,
PCR.SC selects which counter pair is updated (unless PCR.ULRO is set; see below). On
read, PCR.SC selects which counter pair is to be read through PIC (ASR 17).
Defined (as S1) in SPARC JPS1 Commonality.
Defined (as S0) in SPARC JPS1 Commonality.
Implementation-dependent field (impl. dep. #207) that specifies whether SU/SL are
read-only. In SPARC64 V, this field is write-only/read-as-zero, specifying update
behavior of SU/SL on write. When PCR.ULRO = 1, SU/SL are considered as read-only;
the values set on PCR.SU/PCR.SL are not written into SU/SL. When PCR.ULRO = 0,
SU/SL are updated. PCR.ULRO is intended to switch visible PIC by writing PCR.SC,
without affecting current selection of SU/SL of that PIC. On PCR read, PCR.SU/PCR.SL
always shows the current setting of the PIC regardless of PCR.ULRO.
Defined in SPARC JPS1 Commonality.
Defined in SPARC JPS1 Commonality.
0
SC
0
SU
0
21
18
17
16
11
10 9
20
0
FIGURE 5-1
SL
ULRO UT ST PRIV
4
3
2
1
U3
L3
U2
L2
U1
L1
7
6
5
4
3
2
F. Chapter 5
Registers
and
0
U0
L0
1
0
21
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