82870P2P64H2 Datasheet, PDF (172/217 Pages) –

Functional Description
R
Figure 15. 66 MHz PCLK Skew
CLK66
66 MHz PXPCLKI
Tskew (min)
66 MHz PXPCLKI
Tskew (max)
Tskew
(max)
Tskew
(m in)
Clk_skew_66mhz
4.8.2
4.8.2.1
Component Reset
It may take the P64H2 logic up to 128 ms after primary reset deassertion and up to 2 ms after
secondary bus reset deassertion for the PCI buffers to be fully compensated. System BIOS timings
must guarantee that no PCI cycles are attempted on the P64H2 PCI bus during these times.
There are three varieties of reset that could be performed on the P64H2. They are listed from
highest level of reset to the lowest level of reset.
1. PWROK: When this reset is used, RSTIN# must also be asserted. This reset determines the
hot plug mode of operation (no hot plug, single-slot, dual-slot, and multi-slot). This signal
must go inactive at least 1 ms before RSTIN# goes inactive to ensure the PCI bus is in the
proper mode.
2. RSTIN#: This signal is typically connected to the PCIRST# output of the ICHx but can come
from any source. When this pin is asserted, all logic (except the RAS register bits) in the
P64H2 is reset. This reset also causes the PCIRST# output of each PCI interface to be
asserted. The hot plug mode of operation is not affected by this reset.
3. Software setting the PCI Reset bit (bit 6) in the Bridge Control Register: This causes
PCIRST# output of the particular interface to be reset. The hot plug mode, hub interface,
configuration registers, RAS bits, and peer PCI interface are not affected by the assertion of
this bit.
Software PCI Reset
This reset is also caused upon an RSTIN# reset (Section 4.8.2.2) and PowerOK reset. This reset
exists to reset a hung PCI bus, and to change PCI bus frequency. On the active edge of this reset,
the P64H2 changes the PxPCLKO[5:0] frequency to that dictated by bits 8:6 of PCI configuration
offset 40h in the bridge being reset.
If the PCI bus is in single-slot mode and the card is disconnected, the bus is driven to ground as
described in Section 4.3.3.
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Intel^® 82870P2 P64H2 Datasheet