User's Manual

Layout/Routing Guidelines
2-60 Intel
®
820 Chipset Design Guide
2.13.3 Ultra ATA/66 Pullup/Pulldown Requirements
•
22 Ω – 47 Ω series resistors are required on RESET#. The correct value should be determined
for each unique motherboard design, based on signal quality.
•
An 8.2 KΩ to 10 KΩ pull-up resistor is required on IRQ14 and IRQ15 to VCC5.
•
A 10 KΩ pull-down resistor is required on PDD7 and SDD7 (as required by the ATA-4
specification).
•
A 5.6 KΩ pull-down resistor is required on PDDREQ# and SDDREQ# (as required by the
ATA-4 specification).
•
A 1K Ω pull-up resistor is required on PIORDY and SIORDY (as required by the ATA-4
specification).
Figure 2-50. Resistor Requirements for Primary IDE Connector
5.6k
ohm
Reset#
Primary IDE Connector
ICH
10k
ohm
PDD[15:8]
PDD[6:0]
PCIRST_BUF#*
22 - 47 ohm
PDA[2:0]
PDCS1#
PDCS3#
PDIOR#
PDIOW#
PDDREQ
PIORDY
PDD[7]
*Due to ringing, PCIRST# must be buffered.
1k
ohm
5V
470 ohm
CSEL
Pin 34
N.C.
PDDACK#
IRQ14
5V
8.2k-10k
ohm
Pin 32
N.C.