Intel VC820 Design Guide - Page 86
Ultra ATA/66 Pullup/Pulldown Requirements
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Layout/Routing Guidelines 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 PCIRST_BUF#* PDD[15:8] PDD[7] PDD[6:0] PDA[2:0] PDCS1# PDCS3# PDIOR# PDIOW# PDDREQ PIORDY IRQ14 PDDACK# 5V 5V 1k ohm 8.2k-10k ohm 5.6k ohm ICH 22 - 47 ohm Reset# Primary IDE Connector 10k ohm 470 ohm N.C. N.C. CSEL Pin 32 Pin 34 *Due to ringing, PCIRST# must be buffered. 2-60 Intel®820 Chipset Design Guide