82870P2P64H2 Datasheet, PDF (136/217 Pages) –

Functional Description
R
4.3.1.2
Input Control
The input interface captures eight inputs from each slot:
• SLOT SWITCH: Determines whether a slot should be powered. Connected to the slot switch
on the chassis.
• FAULT#: Over-current / Under-volt indication: When asserted, the P64H2, if enabled,
immediately asserts reset and disconnects the slot from the bus.
• PRSNT1# and PRSNT2#: Signals which determine whether or not a card is installed and to
budget system power. These inputs are connected to the PRSNT1# and PRSNT2# pins on the
PCI card.
• M66EN: Determines if a card can be added to the bus without reducing the clock frequency
of the PCI bus.
• PCIXCAP1 and PCIXCAP2: Determines if a slot is PCI-X capable, and if so, whether it can
operate at 133 MHz.
• 1 User-Defined Input: Stored in the Hot plug Non-Interrupt Inputs Register (although
marked as reserved bits 24 through 29.). This is available only in Serial Mode.
4.3.1.3 Stutter Mode
Stutter mode minimizes the amount of external hardware required to implement fewer than six
slots. The stutter mode used corresponds to the number of slots supported by the system. Stutter
mode selection is determined by HP_SLOT[2:0], as shown in Table 37.
Table 37. Stutter Logic Modes
HP_SLOT[2:0]
000
001
010
011
100
101
110
111
# of
Slots
Inputs
Outputs
Hot Plug Disabled
Parallel Mode—No Stutter
Parallel Mode—No Stutter
3
Yes
Yes
4
Yes
Yes
5
Yes
Yes
6
Yes
No
Reserved (Hot plug Disabled)
Figure 3 shows how 6-slot stutter mode serial inputs are sampled. The serial clock stutters at bit
positions 6 and 7, but internally the bit shifted last (bit 5 in this example) is sampled as the next
successively stuttered bits (bit 6 and 7 in this example). This is why in some registers (e.g., the
memory register HMIC) bits for disabled slots take their values from the last enabled slot.
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Intel^® 82870P2 P64H2 Datasheet