Fujitsu Fujitsu SPARC64 V manual Ovf, Ovro

The Performance Control Register in SPARC64 V is illustrated in FIGURE 5-1and described in TABLE 5-2.

0

OVF 0 OVRO 0

NC

0

SC 0 SU 0 SL

ULRO

UT ST PRIV

63		48	47	32 31	27	26	25 24	22	21	20	18	17	16	11 10	9	4	3	2	1	0
			FIGURE 5-1SPARC64 V Performance Control Register (PCR) (ASR 16)
TABLE 5-2PCR Bit Description
	Bit	Field		Description
	47:32	OVF		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.

0

U3 L3 U2 L2 U1 L1 U0 L0

		15	7	6	5	4	3	2	1	0
26	OVRO	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.
24:22	NC	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).
20:18	SC	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).
16:11	SU	Defined (as S1) in SPARC JPS1 Commonality.
9:4	SL	Defined (as S0) in SPARC JPS1 Commonality.

3ULRO 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.

2	UT	Defined in SPARC JPS1 Commonality.
1	ST	Defined in SPARC JPS1 Commonality.

Release 1.0, 1 July 2002 F. Chapter 5 Registers 21