Intel
®
82870P2 (P64H2)
104
Design Guide
8.2.5.3
Debounced Hot Plug Switch Input
The switch inputs (Px_IRQ[15] in this case—see
) to the Hot Plug controller do not
require any debouncing logic in this mode. This logic is contained within the P64H2. The
POWERON value for this input is determined by BIOS. However, it is recommended that BIOS
define a logic 0 to represent that the slot can be powered on.
8.2.5.4
Comparator Circuit for PCIXCAP1/PCIXCAP2 Pins
A comparator circuit is required for properly decoding the PCI/PCI-X capability of the slot. Refer
to the
PCI Local Bus Specification, Revision 2.2
for this circuit. For more information on the
reference circuit, refer to
. The Board Designers could also use
as a
reference.
8.2.5.5
Tri-State Buffer or 2:1 MUX for HPxSLOT [2:0]
The HPxSLOT [2:0] pins are pull-ups/pull-downs for determining the slot count and mode of
operation for the P64H2 Hot Plug Controller. The strapping value on these pins is latched on the
rising edge of PWROK. In Single Slot Parallel Mode, these pins also function as the PCIXCAP1A,
PCIXCAP2A, and PCIXCAP1B inputs to the controller. Logic must exist to preserve the slot count
value when the system is in reset (PWROK signal is low).
It is also possible to accomplish this strapping requirement using a 2:1 MUX. The PWROK signal
can be used to enable the tri-state buffer. The decision is left up to the individual designer on which
method to use. See
for an example of the optional MUX circuit.
Table 8-9. Frequency Matrix
Frequency
M66EN
PCIXCAP1
PCIXCAP2
133EN
PCI 33
0
X
X
X
PCI 66
1
0
0
X
PCI-X 66
X
1
0
X
PCI-X 100
X
1
1
0
PCI-X 133
X
1
1
1
Figure 8-9. Tri-State Buffer Circuit Example
ENB
PCIXCA Px
Input
Decoded PCIXCAP
S ignal from P CI SLO T
Enabled by PW RO K#
1 k
Ω
Summary of Contents for Xeon
Page 24: ...Introduction 24 Design Guide This page is intentionally left blank ...
Page 30: ...Component Quadrant Layout 30 Design Guide This page is intentionally left blank ...
Page 52: ...Platform Clock Routing Guidelines 52 Design Guide This page is intentionally left blank ...
Page 66: ...System Bus Routing Guidelines 66 Design Guide This page is intentionally left blank ...
Page 118: ...Intel 82870P2 P64H2 118 Design Guide This page is intentionally left blank ...
Page 146: ...I O Controller Hub 146 Design Guide This page is intentionally left blank ...
Page 148: ...Debug Port 148 Design Guide This page is intentionally left blank ...
Page 210: ...Schematic Checklist 210 Design Guide This page is intentionally left blank ...
Page 220: ...Layout Checklist 220 Design Guide This page is intentionally left blank ...
Page 222: ...Schematics 222 Design Guide This page is intentionally left blank ...