Intel 815 - Manual (Page 116)

I/O Subsystem
R
116 Intel
®
815 Chipset Platform Design Guide
10.2.3 Primary IDE Connector Requirements
Figure 60. Resistor Schematic for Primary IDE Connectors
5.6 k Ω
Reset#
Pri
m
ar
y ID
E
co
nn
ec
to
r
ICH
10 k Ω
PDD[15:8]
PDD[6:0]
PCIRST_BUF#*
22 - 47 Ω
PDA[2:0]
PDCS1#
PDCS3#
PDIOR#
PDIOW#
PDDREQ
PIORDY
PDD[7]
*Due to ringing, PCIRST# must be buffered.
1 k Ω
5V
470 Ω
CSEL
N.C.
PDDACK#
IRQ14
5V
8.2 k Ω
IDE_resistor_schem_primary
Pin 32
•
Due to the elimination of the ISA bus from the ICH, PCI_RST# should be connected to pin 1
of the IDE connectors as the IDE reset signal. Because of high loading, the PCI_RST# signal
should be buffered.
•
22
Ω
to 47
Ω
series resistors are required on RESET#. The correct value should be
determined for each unique motherboard design, based on signal quality.
•
IRQ14 and IRQ15 each require an 8.2 k
Ω
pull-up resistor to VCC.
•
A 1 k
Ω
pull-up to 5V is required on PIORDY and SIORDY.
•
A 470
Ω
pull-down is required on pin 28 of each connector.
•
A 5.6 k
Ω
pull-down is required on PDREQ and SDREQ.
•
The primary IDE connector uses IRQ14, and the secondary IDE connector uses IRQ15.
•
There is no internal pull-up or pull-down on PDD7 or SDD7 of the ICH. Devices must not
have a pull-up resistor on DD7. It is recommended that a host have a 10 k
Ω
pull-down resistor
on PDD7 and SDD7 to allow the host to recognize the absence of a device at power-up (as
required by the ATA-4 specification).