RTC External Rtcrst Circuit | Intel 820E guide

Intel® 820E Chipset

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A standby power supply should be used in a desktop system to provide continuous power to the RTC when available, which will significantly increase the RTC battery life and thereby increase the RTC accuracy.

2.19.5.RTC External RTCRST Circuit

The ICH2 RTC requires additional external circuitry. The RTCRST# signal is used to reset the RTC well. The external capacitor and the external resistor between RTCRST# and the RTC battery (VBAT) were selected to create an RC time delay, such that RTCRST# will go high some time after the battery voltage becomes valid. The RC time delay should be within the range 10 ms–20 ms. When RTCRST# is asserted, bit 2 (RTC_PWR_STS) in the GEN_PMCON_3 (General PM Configuration 3) register is set to 1 and remains set until cleared by software. As a result, when the system boots, the BIOS knows that the RTC battery has been removed.

Figure 61. RTCRST External Circuit for ICH2 RTC

	VCC3_3SBY
Diode/
Battery
Circuit	1 kΩ
	1 kΩ

8.2 kΩ

RTCRST

Circuit

VccRTC 1.0 µF

RTCRST#

2.2 µF

rtc_rtcrst_ich

This RTCRST# circuit is combined with the diode circuit (Figure 60. Diode Circuit Connecting RTC External Battery), which allows the RTC well to be powered by the battery when system power is unavailable. Figure 59 is an example of the circuit used in conjunction with the external diode circuit.

Design Guide

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Image 99

Intel 820E manual RTC External Rtcrst Circuit, Rtcrst External Circuit for ICH2 RTC

Contents

Design Guide Intel 820E Chipset Intel 820E Chipset Contents 1.1 102 AGTL+ 191 Figures CDCDNENAB# Support Circuitry for Multi-Channel Audio Upgrade Mil Stack-Up Tables 135 Rev Description Date Revision History About This Design Guide Introduction Reference Documents System Overview Chipset Components Memory Controller Hub MCHController Hub 2 ICH2 Intel 820E Chipset Platform Bandwidth Summary FWH Flash BiosBandwidth Summary ISA Bridge MCH System Configuration UltraATA/100/66/33 USB Ports 2 HC AC97 Codecs AGP Platform InitiativesDirect Rambus RAM Rdram Streaming Simd Extensions Manageability Integrated LAN ControllerUltra ATA/100 Support Expanded USB Support Interrupt Controller Function DisableIntruder Detect SMBus 9. AC’97 Ebga C AC’97 Connections Low-Pin-Count LPC Interface This page is intentionally left blank Component Quadrant Layout General Recommendations MCH Sample ATX and NLX MCH/ICH2 Component Placement Intel 820E Chipset Component Placement Primary-Side MCH Core Routing Example ATX Core Chipset Routing Recommendations Secondary-Side MCH Core Routing Example ATX Data Strobing Example Source-Synchronous Strobing Data Associated Strobe Differential Clocking/StrobingDirect RDRAM* Interface AGP 2× Data/Strobe Association Direct RDRAM* Layout Guidelines Stack-Up Placement Guidelines for Motherboard Routing Lengths RSL RoutingReference Trace Description Maximum Trace Length RSL Routing Diagram Secondary-Side RSL Breakout Example Direct Rdram Termination RSL Termination Direct RDRAM* Termination Example Direct RDRAM* Ground Plane Reference GND Plane Plane Equation 1. Approximate Copper Tab Area Calculation Direct RDRAM* Connector Compensation Copper Tab Area Calculation Connector Compensation Example Section a See Note, Top Layer Section a See Note, Bottom Layer Section B See Note, Top Layer Section B See Note, Bottom Layer RSL and Clocking Signal Routing Layer Capacitance pF Flood Signal RSL Signal Layer Alternation RSL Routing Layer Requirements Length Matching Methods Equation 3. Rdram Clock Signal Trace Length Calculation Equation 2. Rdram RSL Signal Trace Length Calculation Length Matching and Via Compensation Example Via Compensation Signal Ball on Nominal Package High-Speed Cmos Routing Direct RDRAM* Reference Voltage High-Speed Cmos Termination SIO Routing Rdram Cmos Shunt Transistor Suspend-to-RAM Shunt Transistor Direct RDRAM* Clock Routing Direct RDRAM* Design ChecklistSignal List RSL Signals High-Speed Serial Clocks Intel 820E Chipset Primary side If Signal Routed from MCH AGP AGP Interface Signal Groups Signal Groups AGP 2.0 Data/Strobe Associations 2 × Timing Domain Routing Guidelines3 ×/4× Timing Domain Routing Guidelines Interfaces 6 Inches AGP 2×/4× Routing Example for Interfaces 6 Inches Interfaces 6 Inches and 7.25 Inches AGP 2.0 Routing Summary1,2 Signal Maximum Trace Spacing Length Relative ToAGP 2.0 Routing Summary All AGP Interfaces Decoupling AGP Clock RoutingGeneral AGP Routing Guidelines Recommendations Ground Reference Vddq Generation and TYPEDET# TYPEDET# on Add-in Card DDQ Supplied by MB TYPDET#/VDDQ Relationship AGP Vddq Generation Example Circuit Vref Generation for AGP 2.0 2× and 4× AGP 2.0 Vref Generation and Distribution Compensation AGP Pull-Ups16 k Ω Motherboard / Add-in Card Interoperability AGP Signal Voltage Tolerance ListConnector / Add-in Card Interoperability Connector Universal Connector AGP Left-Handed Retention Mechanism AGP Universal Retention Mechanism RM AMP P/N AGP Left-Handed RM Keep-Out Information Hub Interface Hub Interface Signal Routing Example Bit Hub Interface Routing Guidelines Bit Hub Interface Data SignalsBit Hub Interface Strobe Signals Bit Hub Interface Buffer Configuration Setting MCH ICH2 Hlrefa Hubref Bit Hub Interface Hubref Generation Circuit Specifications Component Hub Interface Trace Rcomp Resistor Value Bit Hub Interface CompensationBit Hub Interface Decoupling Guidelines Bit Hub Interface Rcomp Resistor Values Additional Host Bus Guidelines System Bus Ground Plane ReferenceMinimizing Crosstalk on the AGTL+ Interface IDE Interface Additional ConsiderationsCable Combination Host-Side/Device-Side Cable Detection Cable Detection for Ultra ATA/66 and Ultra ATA/100 Combination Host-Side/Device-Side IDE Cable Detection Device-Side IDE Cable Detection Device-Side Cable Detection Primary IDE Connector Requirements Secondary IDE Connector Requirements SDCS1# SDCS3# SDIOR# SDIOW# SddreqSiordy IRQ15 SDDACK# ICH2 AC’97- Codec Connection 13. AC’97 Intel 820E Chipset Motherboard CNR Board CNR Signal Descriptions AC97RESET#CDCDNENAB# Invalid Codec Configurations Valid Codec ConfigurationsCodec Configurations Valid Codec Configurations 13.3. AC’97 Routing Using Native USB Interface USBMotherboard Implementation Recommended USB trace characteristics ISA SupportDisabling the Native USB Interface of ICH2 SMBus/SMLink Interface 16. I/O Apic Design Recommendation SMBus / SMLink Use Implementation Pull-Up Requirements for SMBus and SMLink Signals RTC PCI External Capacitors RTC Crystal RTC Layout Considerations RTC External Battery Connection Rtcrst External Circuit for ICH2 RTC RTC External Rtcrst Circuit RTC-Well Input Strap Requirements Spkr Pin ConsiderationRTC Routing Guidelines Vbias DC Voltage and Noise Measurements Function in ICH2 using the PCI IRQ in Ioapic ICH2 Pirq RoutingUsage of I/O Apic Interrupt Inputs 16 through PIRQE# PIRQF# PIRQG# PIRQH# Inta Intb Intc Intd LAN Connect Component Connection FeaturesLAN Layout Guidelines PIRQA# PIRQB# PIRQC# PIRQD# ICH2 LAN Interconnect Guidelines LAN Design Guide Section ReferenceLayout Section Previous Design Guide Section Bus Topologies Point-to-Point InterconnectLOM/CNR Interconnect Signal Routing and Layout ConfigurationLength Requirements for Figure Crosstalk Consideration ImpedancesLine Termination General Trace Routing Considerations General LAN Routing Guidelines and Considerations Trace Geometry and Length Power and Ground Connections Ground Plane Separation Layer Board Design Design Guide 111 Related Documents Guidelines for Intel 82562EH Component PlacementIntel 82562EH Home/PNA* Guidelines Crystals and Oscillators Intel 82562EH Component Termination Phoneline Hpna Termination Distance Priority Guideline Critical DimensionsLPF Eeprom Distance from LPF to Phone RJ11 Intel 82562ET / Intel 82562EM Component Guidelines Intel 82562ET/82562EM Component Termination Distance from Magnetics Module to RJ45 Terminating Unused Connections Reducing Circuit Inductance LAN Disable Circuit Intel 82562ET/EM Disable Guidelines Lancl Dual-Footprint Analog Interface Power Plane/Pins # Decoupling Capacitor Value ICH2 Decoupling RecommendationsDecoupling Capacitor Recommendation Decoupling Capacitor Layout FWH Flash Bios Guidelines In-Circuit FWH Flash Bios ProgrammingFWH Flash Bios VPP Design Guidelines ICH2 Design Checklist Checklist Items Recommendations Reason/EffectPCI Interface Eeprom Interface FWH Flash Bios InterfaceHub Interface LAN Interface PIRQ#E Interrupt InterfacePIRQ#DA PIRQ#H Gpio USB InterfaceVCCSUS3.3 Processor Signals System Management RTCAC’97 5VREF SUS Miscellaneous SignalsPower Spkr IDE Checklist ISA Bridge Checklist Checklist ItemsICH2 AD22 / ISA USB ICH2 Layout ChecklistBit Hub Interface IDE Interface LAN Connect I/F ICH2 Decoupling Layout Recommendations Yes CK-SKS Clocking 138 Design Guide Term Definition Terminology and Definitions 140 Design Guide Guideline Methodology AGTL+ Design Guidelines Equation 6. Maximum Flight Time Equation 4. Setup TimeInitial Timing Analysis Equation 5. Hold Time IC Parameters Pentium Intel AGTL+ Parameters for Example Calculations1,2 Driver Receiver Clk Example Tfltmax Calculations for 133 MHz Bus1 Sensitivity Analysis Determine the Desired General Topology, Layout, and RoutingPre-Layout Simulation Methodology Simulation Criteria Monte Carlo Analysis Estimate Component-to-Component Spacing for AGTL+ Signals Place and Route BoardLayout and Route Board Host Clock Routing Apic Data Bus Routing Trace Width Space GuidelinesCrosstalk Type Trace WidthSpace Ratio Post-Layout Simulation Intersymbol Interference Validation Crosstalk AnalysisMeasurements Flight Time Simulation Equation 8. Valid Delay Equation Flight Time Hardware ValidationSET Q CLR Q Theory AGTL+Timing Requirements Aggressor and Victim Networks Crosstalk Theory Potential Termination Crosstalk Problems Textbook Timing Equations More Details and Insight Effective Impedance and Tolerance/Variation Power Distribution Reference Planes and PCB Stack-Up One Signal Layer and One Reference Plane Layer Switch with Multiple Reference Planes Same Type One Layer with Multiple Reference Planes High-Frequency Decoupling Clock Routing Vref Guard Band Ringback LevelsOverdrive Region Flight Time Definition and Measurement Conclusion Clock Generation Intel 820E Chipset Platform System ClocksNumber Name on CK133 Used for Routed to Frequency Voltage Intel 820E Chipset Platform Clock Distribution Intel 820E Chipset Platform Clock Skews Relationship Skew Pin-to-Pin ps Board ps Total ps Min MaxLPCCLK, Pciclk ±TBD3 Intel 820E Chipset Clock Routing Guidelines1,2 CK133/DRCG Pin Name Component Intel 820E Chipset Platform System Clock Cross-Reference Component Placement and Interconnection Layout Requirements 1 .318 MHz Crystal to CK1332. CK133 to Drcg MCH to Drcg MCH-to-DRCG Routing Diagram Clock From Length inches Section DRCG-to-RDRAM ChannelTrace Length Trace Geometry Differential Clock Routing Diagram Sections A, C & D CMID, CMID2 Drcg Impedance Matching CircuitExternal Drcg Component Values1,2 Component Nominal Value Drcg Layout Example AGP Clock Routing GuidelinesClock Routing Guidelines for Intel PGA370 Designs Series Termination Resistors for CK133 Clock Outputs Buffer Name CC Range Impedance If Unused Output Unused OutputsDecoupling Recommendation for CK133 and Drcg Unused Output Termination Drcg Frequency Selection and the DRCG+ Drcg Frequency Selection Table and Jitter Specification DRCG+ Frequency Selection DRCG+ Frequency Selection Schematic PCB Materials Stack-Up Requirement Test Coupon Design Guidelines Design Process Sample SM max Resin % Recommended Stack-UpInner-Layer Routing Stack-Up Examples Field Solver vs. Zcalc Impedance Calculation Tools Board Impedance/Stack-up Summary Testing Board Impedance 182 Design Guide Power Delivery Terminology and DefinitionsTerm Definition Intel 820E Chipset Power Delivery Example VCC Dual Switch Vbsy 3VSB V and 2.5 V Power Sequencing Schottky Diode VSB ICH2 1.8 V / 3.3 V Power Sequencing 4 .3V/V5REF Sequencing Example 1.8V/3.3V Power Sequencing Circuit Excessive Power Consumption by 64/72-Mbit Rdram Option 1 Reduce the Clock Frequency During InitializationVref Use a GPO to Reduce Drcg Frequency Example of ICH2 Power Plane Split ICH2 Power Plane Split Component Thermal Design Power 133/400 MHz Thermal Design PowerFeatures Intel 820E Chipset Component Thermal Design Power Vendor Intel Contact Contact Information Glue Chip Vendors Reference Design Feature Set Appendix a Reference Design Schematics Uniprocessor 196 Design Guide FOLSOM, California Last Revised Sheet REVDrawn by PCG Platform Design Project PCG AE Prairie City Road Device Table Block Diagram AL9 AK8AH8 AN9 Tckr TDI Tmsr CPURST#R2 DBRESET#VCMOS15 Gtlref Clock Synthesizer Hubref Agpref Ramrefb Ramrefa Gtlrefb Gtlrefa Host Hubref RamrefrRamref Connagpref GAD2 GAD3 GAD0GAD0 GAD1 GAD1 GAD2 AD3 AD0AD1 AD2 Rtcrstjp ACRESET#CR4 Vbatcr 1UF VCC10 VCC31 Vppr VPP GND30 PCIRST# GND29 NC1 GndaFwhic Vcca LFRAME#/FWH4 NC3 NC4 INIT# HINIT# NC5 RFU36 NC6 RFU35 FGPI4 RFU34 NC8 RFU33 Fwhpclk CLK RFU32 Rimm LDQA0 SWP RSRV4/RESETRSRV4/RESET SWP TERMDQA80 Super I/O AC’97 Audio DB15AUDSTK Micinr MicinfbMicin Micinc Communication And Network Riser CNR ACSDATAIN0CNR Acsynccnr Acsdataoutcnr Stubs on AC97 LinkACSDATAIN0ICH2 ACSYNCICH2 ACSDATAOUTICH2 RP7 LAN 82562EH 82562ET/EM LAN RJ11 For 82562EH LAN RJ45 For 82562ET/EM H1138ARAGONITELanactled LAN Option Intel PART# 25MHZY5 Xtal Y2 Xtal LANCLKX1 R381LANCLKX2 Stuff for 82562EH VCC12 Irtx Power SWPower LED SW1 Agpclkconn B7 CLK AGP4XU20 AGPOC#TYPEDET# USBAGP+ B4 Usbagp Ptdi VCC5 VCC12PCI3CON PTRST# Ptck Ptms PCI Connectors IDE Connectors USB Connectors Port Parallel Serial Ports Keyboard/Mouse/Floppy VCC5 JOY1XR JOY2XR Midioutr JOY2YR JOY1YR Midiinr Game Port Imax VRM G1 VRM G2 VRM Fault VRM IFBFAULT# IFB Vccvid REV Project Voltage Regulators SBY ITH R 1UF-X7RVCC33SBYTG VCC33SBYSW VCC25SBY VCC5DUAL VCC33SBY VCC33SBYCOSC VCC33SBYRUN VCC33SBYITH Power Connector HREQ#0 BPRI# DBSY# PCI/AGP Pullups/Pulldowns Termcmd Termsck Rambus* Termination Decoupling Bulk Decoupling Drawn by PCG Platform Design Project PCG AE VCMOS18SBY Revision History Drawn by PCG Platform Design Project PCG AE Revision History HL8 HL4 HL5 HL6 HL7 Hub Interface Connector For debug onlyProbe Connector TESTCLK66 HL0 HL1 HL2 HL3 HL9 Hlstb HLSTB#