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8/01/00
Am79C976
119
P R E L I M I N A R Y
ister, which can be loaded from the serial EEPROM. It
is recommended that the shadow register be pro-
grammed to a value of 18h, which corresponds to 6 μs.
The host should use the value in this register to deter-
mine the setting of the PCI Latency Timer register.
The PCI MIN_GNT register is read only.
0#A@<
Offset 3Fh
The PCI MAX_LAT register is an 8-bit register that spec-
ifies the maximum arbitration latency the Am79C976
controller can sustain without causing problems to the
network activity. The register value specifies the time in
units of 1/4 μs. The MAX_LAT register is an alias of the
Maximum Latency Shadow Register, which can be load-
ed from the serial EEPROM. It is recommended that the
shadow register be programmed to a value of 18h,
which corresponds to 6 μs.
The host should use the value in this register to deter-
mine the setting of the PCI Latency Timer register.
The PCI MAX_LAT register is read only
0'5$
Offset 44h
Bit
Name
Description
7-0
CAP_ID
This register identifies the linked
list item as being the PCI Power
Management registers. This is a
read-only register whose value is
fixed at 1h.
0&!0
Offset 45h
Bit
Name
Description
7-0
NXT_ITM_PTR
The Next Item Pointer Register
points to the starting address of
the next capability. The pointer at
this offset is a null pointer, indi-
cating that this is the last capabil-
ity in the linked list of the
capabilities. This is a read-only
register whose content is fixed at
0.
008#!'5
:0#;
Offset 46h
Note:
All bits of this register are loaded from
EEPROM. The register is aliased to BCR36 for testing
purposes.
Bit
Name
Description
15-11
PME_SPT
PME Support. This 5-bit field indi-
cates the power states in which
the function may assert PME. A
value of 0b for any bit indicates
that the function is not capable of
asserting the PME signal while in
that power state.
Bit(11) XXXX1b - PME can be
asserted from D0.
Bit(12) XXX1Xb - PME can be
asserted from D1.
Bit(13) XX1XXb - PME can be
asserted from D2.
Bit(14) X1XXXb - PME can be
asserted from D3hot.
Bit(15) 1XXXXb - PME can be
asserted from D3cold. The value
read from bit(15) is the AND of
the value of BCR36, bit 15 and
the
current
VAUX_SENSE pin.
state
of
the
Read only.
10
D2_SPT
D2 Support. If this bit is a 1, this
function supports the D2 Power
Management State.
Read only.
9
D1_SPT
D1 Support. If this bit is a 1, this
function supports the D1 Power
Management State.
Read only.
8-6
RES
Reserved locations. Written and
read as zeros.
5
DSI
Device
When this bit is 1, it indicates that
special initialization of the func-
tion is required (beyond the stan-
dard PCI configuration header)
before the generic class device
driver is able to use it.
Specific
Initialization.
Read only.
4
RES
Reserved location. Written and
read as zero.