system management bus revision 2 - smart battery system · 02-04-1999 · smbus revision 2.0 r....
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SMBus Revision 2.0 R. Dunstan, Intel and D. Stolitzka, ADI
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System Management BusRevision 2.0
Robert Dunstan, Intel CorporationDale Stolitzka, Analog Devices, Inc.
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SMBus Revision 2.0 R. Dunstan, Intel and D. Stolitzka, ADI
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Agenda
• Why make an SMBus 2.0--An Overview?• PCI Engineering Change Request• Electrical Specifications
• DC / AC
• Protocol Layer• ARP, the address resolution protocol• Packet Check Coding
• Impact on the SBS IF
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SMBus Revision 2.0 R. Dunstan, Intel and D. Stolitzka, ADI
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Why make an SMBus 2.0?
• Desktop and Server Needs• PCI Bus Engineering Change Request
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SMBus Revision 2.0 R. Dunstan, Intel and D. Stolitzka, ADI
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Desktop OEM’s Made TheseComments on SMBus• SMBus has become an extremely popular
bus for connecting low-speed components toeach other
• SMBus attaches these devices• EEPROMs, sensors, latches, monitoring ASICs
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SMBus Revision 2.0 R. Dunstan, Intel and D. Stolitzka, ADI
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Desktop OEMs Use SMBus...
• Configuration or Inventory Applications• DIMMs/RIMMs Memory Modules• Clock Generators• Identify a Slot 2 Processor by Type and Speed• EEPROM contain vital product data• Digital Potentiometers
• System Monitoring• Temperature Monitors• Fan Control• Environmental Monitoring• Security
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SMBus Revision 2.0 R. Dunstan, Intel and D. Stolitzka, ADI
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SMBus Devices in Systemsthat are in Production Today• Memory DIMMs (3 EEPROMs)• ISC 9179 clock generation control• Inventory for Slot 2 Processor Type/Speed• EEPROM for vital product data• Voltage/Fan monitoring, e.g., ADM9240
• Processor Temperature , e.g., ADM1021
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SMBus Revision 2.0 R. Dunstan, Intel and D. Stolitzka, ADI
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Electrical Specifications, v2.0
• New DC Electrical specifications allow:• Driving SMBus signals through PCI connector• Multiple loads on a planar (motherboard)• Suitable for desktop and mobile environments
• AC specifications include some noiseimmunity tolerance from DC to 10MHz
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SMBus Revision 2.0 R. Dunstan, Intel and D. Stolitzka, ADI
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Protocol Layer Outline
• ARP (Address Resolution Protocol)• An ARP is the ability for a device to accept a new
SMBus address through a sequence ofcommands
• ARP commands in the command set• Other commands outside of the ARP
• Hot-plug issues• Packet check coding is required
• CRC-8: C(x) = x8 + x2 + x1 + 1
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SMBus Revision 2.0 R. Dunstan, Intel and D. Stolitzka, ADI
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SMBus 2.0 ARP
• Needs of SMBus devices on PCI cards aredifferent from motherboard components:• No past knowledge of devices (address/types)• Similiar PCI cards can result in several device of
the same type plugging into the PCI bus• SMBus ver 2.0 requires PCI card devices to
accept new bus addresses
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SMBus Revision 2.0 R. Dunstan, Intel and D. Stolitzka, ADI
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SMBus 2.0 AddressResolution Protocol Highlights• Notification
• Devices may request enumeration on power-up
• Discovery• OS can discover devices
• discover and identify devices• assign addresses and access the devices
• Other entities can discover devices• Secondary hosts can discover devices on the bus
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SMBus Revision 2.0 R. Dunstan, Intel and D. Stolitzka, ADI
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Hot-plug & SMBus
• Servers hot-plug PCI cards so that new orreplacement cards do not interrupt service
• Mobile systems hot-plug into a dock• SMBus is appropriate for hot-plugging
• Bus is being hot-plugged for batteries• However, there are complex power-up issues
• ECR plans to use existing PCI quick switches• Servers may use SMBus when the PCI is not
operating (a sideband to the PCI bus)
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SMBus Revision 2.0 R. Dunstan, Intel and D. Stolitzka, ADI
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AOL use of SMBus
• Current AOL (Alert-On-LAN) implementationsare geared towards LOM (LAN OnMotherboard) solutions• Not friendly if using only the PCI connector
• SMBus is viewed as an interface betweenalert generators and the LAN controller• Unfortunately the NIC (Network Interface Card)
solution is not satisfactory
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SMBus Revision 2.0 R. Dunstan, Intel and D. Stolitzka, ADI
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A solution for NICs
• Need for a cable-less solution for the NIC• Don’t want to repeat the mistakes learned
from Wake On LAN• Initial WOL implementations required a cable
between NIC and the motherboard for wake signaland Vaux power
• Later added PME and 3.3Vaux to the PCI Spec• AOL needs outbound communication even when the OS
is absent. (PME is an inbound signal)
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SMBus Revision 2.0 R. Dunstan, Intel and D. Stolitzka, ADI
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PCI ECR for Adding SMBus
• Effort championed by Compaq, Intel and IBM• Assistance from Analog Devices, Philips, USAR,
3Com
• ECR currently in review by the PCI SIG
• ECR defines SMBus clock and data signalson PCI connector using two reserved pins• Discovery mechanism required!
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SMBus Revision 2.0 R. Dunstan, Intel and D. Stolitzka, ADI
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SMBus Device Discovery
• Existing SMBus specifications do not addressenumeration or dynamically assigned deviceaddresses
• SMBus 2.0 defines an Address ResolutionProtocol (ARP) which provides thesecapabilities
• ARP includes a data structure much like PCIconfiguration space and a unique identifier
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SMBus Revision 2.0 R. Dunstan, Intel and D. Stolitzka, ADI
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More Uses--SMBus over PCI
• Provides the physical backbone for IPMI(Intelligent Platform Management Interface)
• Allows intelligent adapters to enumeratemanageability and instrumentation devices
• Related interfaces (AGP, Mini PCI) to followthe PCI lead
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SMBus Revision 2.0 R. Dunstan, Intel and D. Stolitzka, ADI
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SMBus 2.0 Timeline
• ARP definition 80% complete• Electrical additions to support PCI ECR are
90% complete• 0.9 spec available for public review in April• PCI ECR ratification expected in 2Q99
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SMBus Revision 2.0 R. Dunstan, Intel and D. Stolitzka, ADI
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Summary
• Industry needs an SMBus solution today• SBS IF has developed an interim solution• SMBus is not just a battery bus• The SMBus is still evolving
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SMBus Revision 2.0 R. Dunstan, Intel and D. Stolitzka, ADI
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Impact on the SBS IF (1)
• New influence from Desktop systems• New influence from Server systems• Many problems being solved with the SMBus
different from the original [mobile] vision
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SMBus Revision 2.0 R. Dunstan, Intel and D. Stolitzka, ADI
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Impact on the SBS IF (2)
• Effect on the SBS IF is very positive• Broader endorsement of SMBus• More volume and standardization will lead to
more vendors, wider device selection, moreparticipation in the IF
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SMBus Revision 2.0 R. Dunstan, Intel and D. Stolitzka, ADI
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Conclusions
• SMBus continues to evolve• ARP adds flexibility• Electrical changes make SMBus more usable
on motherboards• Wider influence establishes SMBus as very
important to the PC industry
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SMBus Revision 2.0 R. Dunstan, Intel and D. Stolitzka, ADI
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Call to Action
• Review and comment on specification• email to: [email protected]
• Work with the SBS-IF to make SMBus 2.0successful too!
• Support SMBus in future ACPI OS releases