Trace Length Limits, PCI Clock Routing Guidelines | Intel IXP43X

Hardware Design Guidelines—Intel®IXP43X Product Line of Network Processors

Figure 24. PCI Clock Topology

			PCI Devices
	A	B
	Rs
33 MHz	Clock
33 MHz	Driver
	A	B
	Rs
			Intel®
	A	B	IXP43X
	A	B	Product Line
	Rs		of Network
			Processors
			B4114 -004

Table 23.	PCI Clock Routing Guidelines

	Parameter	Routing Guidelines

	Signal Group	PCI Clock

	Topology	Point-to-Point

	Reference Plane	Ground

	Characteristic Trace Impedance	55 Ω ±10%

	Nominal Trace Width	5 mils

	Nominal Trace Separation	10 mils

	Spacing to Other Groups	20 mils

	Trace length A	Maximum 300 mils

	Trace length B	There is no limit as long as the trace length is maintained for
	Trace length B	each clock and that maximum clock skew is not violated.
		each clock and that maximum clock skew is not violated.

	Resistor Rs	22 Ω ±10%

	Maximum VIAS	6

6.3.1Trace Length Limits

Maximum trace lengths can be calculated for specific speeds at which the bus is intended to run. The limitations of the maximum trace length can be calculated with the equations shown in Section 6.2. Solve for TPROP and use it to calculate the maximum trace length. This is a straight-forward calculation, but very critical to meet timing. It is recommended to keep the trace lengths as short as possible and not to exceed TPROP.

Note: For acceptable signal integrity at up to 33 MHz, it is very important to design the PCB board with controller impedance in the range of 55 Ω ±10%.

	Intel® IXP43X Product Line of Network Processors
April 2007	HDG
Document Number: 316844; Revision: 001US	69

Image 69

Intel IXP43X manual Trace Length Limits, PCI Clock Routing Guidelines

Contents

Hardware Design Guidelines Intel IXP43X Product Line of Network Processors Intel IXP43X Product Line of Network Processors HDGApril Contents Figures Tables Document Number 316844 Revision 001US § § Date Revision Description001 Initial release HDG Chapter Name Description Content Overview Acronyms Related DocumentationList of Acronyms and Abbreviations Sheet 1 Term Explanation List of Acronyms and Abbreviations Sheet 2 Overview HDG Intel IXP435 Network Processor Block Diagram Typical Applications System Memory Map System Architecture Description Intel IXP43X Product Signal Type Definitions Soft Fusible FeaturesSoft Fusible Features Sheet 1 Symbol Description USB Host Each USB can be Enable separately Soft Fusible Features Sheet 2DDRII/I Sdram Interface Ethernet DDRII/I Sdram Interface Pin Description Sheet 1 Signal InterfaceType Name Device-Pin Connection Terminatio Description Field DDRII/I Sdram Interface Pin Description Sheet 2 DDRII/I Sdram Initialization Expansion Bus Signal Recommendations Sheet 1 Expansion BusType Pull Name Recommendations Field Down Expansion Bus Signal Recommendations Sheet 2 Reset Configuration StrapsBoot/Reset Strapping Configuration Sheet 1 Name Type Pull Recommendations Field Down Boot/Reset Strapping Configuration Sheet 2 3 8-Bit Device Interface Setting Intel XScale Processor Operation SpeedIntel XScale Processor Cfg0 Cfg1 Cfgenn Actual Core Speed MHz 4 16-Bit Device Interface 16-Bit Device Interface Flash Interface Flash Interface Example Uart Interface Uart Signal Recommendations Uart Interface Example MII Interface Signal Interface MII MII NPE a Signal RecommendationsMII NPE C Signal Recommendations Sheet 1 MII NPE C Signal Recommendations Sheet 2 MAC Management Signal Recommendations NPE a and NPE CDevice Connection, MII MII Interface Example Gpio Interface Gpio Signal Recommendations USB InterfaceDesign Notes Name Type Pull Description Field Down USB Host Signal Recommendations Common Mode Choke Host Device Utopia Level 2 Interface Utopia Level 2/MIIAType Pull Name Description Field Down UTPOPDATA75 UTPOPDATA4UTPOPADDR40 Utpopfci Utpipfci ClavUtpipsoc ETHARXDATA30 Etharxclk UTPIPDATA6 UTPIPDATA5UTPIPDATA7 UTPIPADDR40 Device Connection HSS Interface HSSTXDATA0 High-Speed, Serial InterfaceHSSTXCLK0 HSSRXDATA0 HSS Interface Example SSP Interface Synchronous Serial Peripheral Port Interface Serial Flash and SSP Port SPI Interface Example PCI Interface PCI Controller Sheet 1 PCI Controller Sheet 2 PCI Interface Block DiagramPciintan Pciclkin PCI Option Interface Connect signal to same pin between PCI Parity Two devicesPCI Host/Option Interface Pin Description Sheet 1 Type Option Description Name Device-Pin Connection Field Signal PCIREQN0 to one PCIREQN30 inputs to the Host On the Option device, these signals are notPCI Host/Option Interface Pin Description Sheet 2 Type Option Name Device-Pin Connection Description Field PCI Host/Option Interface Pin Description Sheet 3 Jtag Interface Clock Signals Clock SignalsInput System Clock Clock Oscillator Recommendations for Crystal Selection Power Power SupplyNominal Name Voltage Description Reset Timing Power SequenceDecoupling Capacitance Recommendations VCC Decoupling § § PCB Overview Component PlacementGeneral Recommendations Component Selection Stack-Up Selection Component Placement on a PCB Controlled-impedance traces Low-impedance power distribution Layer Stackup General Layout Guidelines General Layout and Routing Guide General Component Spacing Signal Changing Reference Planes Good Design Practice for VIA Hole Placement Pad-to-Pad Clearance of Passive Components to a PGA or BGA Clock Signal Considerations MII Signal Considerations USB V2.0 ConsiderationsCrosstalk Power and Ground Plane EMI Design ConsiderationsTrace Impedance § § Topology Electrical Interface@33 MHz Tcyc = 30 nSec Tval = 11 nSec Tprop = 10 nSec Clock Distribution PCI Address/Data Routing GuidelinesParameter Routing Guidelines PCI Clock Routing Guidelines Trace Length Limits Routing Guidelines Signal Loading Introduction Ddrii / Ddri Sdram Group Signal Name Description DDRII/I Signal GroupsDrasn / Ddrrasn Dcasn / Ddrcasn DDR Sdram Supported Ddrii 32-bit Sdram Configurations Supported Ddri 32-bit Sdram ConfigurationsSupported Ddri 16-bit Sdram Configurations Sizea DDRII/DDRI Rcomp and Slew Resistances Pin Requirements Supported Ddrii 16-bit Sdram ConfigurationsAddress Size Leaf Select Total Technology Arrangement Banks DDR-II Symbol Parameter Units Min Max Ddrii OCD Pin RequirementsDDR Clock Timings DDR Sdram Write Timings Symbol Parameter Minimum Nominal Maximum Units DDRII-400 MHz Interface -- Signal Timings Symbol Parameter Minimum Nom Maximum Units DDR II/I Sdram Interface -- Signal TimingsTiming Relationships Printed Circuit Board Layer Stackup Signal Package Lengths Sheet 1 Group Signal Name Length milTiming Relationships Signal Package Lengths Sheet 2 Clock Group Signal Package Lengths Sheet 3 Parameter Definition Data and Control Groups DCB70/DDRCB70, DDQ310 / DDRDQ310 Ddrii Data and Control Signal Group Routing Guidelines Signal Group Members Ddrii Command Signal Group Routing Guidelines § §