NASA SpaceWire Architectures: Present

1
NASA SpaceWire ArchitecturesPresent Future

• Glenn Parker Rakow
• NASA Goddard Space Flight Center
• 2006 MAPLD International Conference
• Washington, D.C.
• September 25, 2006

2
Current SpaceWire Architectures Swift Data Flow

• SpaceWire point-to-point links
• 16 links from segmented detector array readout
  Electronics to Instrument CDH
• Science Data Commands
• PCI
• Instrument CDH to Memory
• Memory to DSP
• MIL-STD-1553
• CMD bus to Spacecraft

3
Current SpaceWire Architectures LRO Data Flow

• Routed SpaceWire traffic
• End-node routers on CDH boards
• Used as Serial backplane
• Single Board Computer Board
• Instrument Interface Board
• S-Band Communication Board
• Ka-Band Communications Board
• Interface to moderate rate instruments
• Not memory mapped like RMAP or GAP
• Side band signaling using Time-Codes
• 1pps
• Barker code detect uplink
• Upper level flow control on downlink frames
• MIL-STD-1553
• Interface to spacecraft subsystem
• Used for low-rate heritage instruments

Instr
A
Instr
B
Instr
A
Instr
B
Xpndr
Xpndr
Instr
C
Instr
C
Hi
-
Rate
Hi
-
Rate
HGA
HGA
SpaceWire
Xmtr
SpaceWire Router
Xmtr
SpaceWire
SpaceWire
Low Rate/
Low Rate/
Unique
Low
-
Rate
Unique
serial bus
serial bus
SpaceWire
SpaceWire
SpaceWire
SpaceWire
SpaceWire
SpaceWire
SpaceWire Router
SpaceWire Router
Router
Router
Router
Router
High
High
Power
Power
Low rate
Low rate
Processor
Processor
Memory
rate
Memory
rate
IO
IO
Supply
Supply
Comm
Comm
Comm
Comm
Parallel Bus
Parallel Bus
Parallel Bus
Backplane
Backplane
CDH
CDH
4
Current SpaceWire Architectures JWST Data Flow
FPE 2
FPE 3
FPE 4
FPE 5
5
Current SpaceWire Architectures

• JWST
• Routed SpaceWire traffic
• From 4 instruments to local router to end node
  router (Instrument CDH ICDH) (cable)
• ICDH end node router to hardware processors (same
  box over backplane)
• Hardware processors to compression engine (same
  box over backplane)
• Compression engine to recorder (cable)
• GOES-R Point-to-point links
• Instrument - CDH with Reliable Data Delivery
  Protocol

6
Traditional Systems

• Different physical interfaces using different
  protocols that require unique hardware and
  software to bridge between them
• Serial interface at one point per enclosure _at_ NIC
• Extra board area and more power for multiple
  interfaces
• Only boards in same enclosure have memory mapped
  access via arbitration
• Enclosures represent limited access
• Reuse reconfigurability limited

Purple
Red
Black
Purple
Blue
Purple
Black
7
Future Systems
Blue
Blue
Blue
Lt. Blue
Red
Red
Blue
Blue
Blue

• Same protocols supported across both physical
  interfaces SpaceWire and SpaceFibre
• Bridged by hardware router
• Low-level protocols (RMAP GAP) for memory
  mapped DMA or single transactions no software
  required blurs enclosure boundaries
• Plug and Play network mapping and
  Change-of-Status indication supported in hardware
• Coming soon!
• Tunnel higher layer protocols

Lt. Blue
Blue
Red
Hardware bridge Between SpaceWire SpaceFibre
Legend
Red SpaceFibre (optical or copper)
Blue SpaceWire
Lt Blue Local port interface (parallel)
8
Advantages

• One communications infrastructure
• Simplifies system design
• Consists of 2 different physical layers
• SpaceWire
• SpaceFibre
• Bridged in hardware via routing switch
• Seamless integration
• Supports low-level high-level protocols
• Virtual serial backplanes
• RMAP GAP
• Upper layer protocol may be identified
• Via Protocol ID (PID)
• Low latency bus
• Wormhole routing
• Side-Band signaling
• Reducing number of interfaces
• Time-Code enhancements
• Pending
• May be used as a time-triggered or event
  triggered bus

9
System Engineer Toolkit

• Router blockage prevention
• Time-out
• Max length

• Buffers match packet size
• Optimize throughput

• Full Duplex
• Cmd Tlm opposite directions

• Priority routing

• Dedicated link for low latency

• SpaceFiber (cell based virtual channels)
• Long distance
• Isolation
• EMC/EMI
• Bridge to SpW via hardware router

• SpaceFiber
• High Rate
• Group Adaptive Routing
• Across multiple SpW links

• Redundant cables

TLM
CMD

• Multiple SpW local ports to prevent blocking
  increase throughput

• Redundant paths

• Message sharing
• Time-critical network
• Consensus computing

• Time-codes
• Near zero-jitter across entire network
• Synchronization
• TDMA
• 1 pps
• Time-Code expansion
• Interrupts
• Polling
• Multi-TimeCode

• Group Adaptive Routing
• Multiple SpW links

10
Conclusions

• Simple protocol that is being developed from
  bottom up to meet advanced spacecraft
  applications
• One bus standard can meet requirements
• Real time control
• Large data throughput
• Safety
• Guaranteed Low latency
• High reliability
• Reuse reconfiguration of systems easier with
  standard interface
• Modular functions with standard interface
• Serial interface
• cable
• backplane
• Provide system engineers more tools for more
  efficient designs