1. 12006 MAPLD International ConferenceSpaceWire 101 Seminar Reliable Data Delivery Protocol (RDDP) William Anderson MEI Technologies Inc. 2006 MAPLD International Conference Washington, D.C. September 25, 2006

2. 22006 MAPLD International ConferenceSpaceWire 101 Seminar Reliable Data Delivery Protocol (RDDP) Introduction Purpose –Provide a means of ensuring correct packet delivery from source to destination by Acknowledgement from receiver Selective Retransmit based on ACK timeout –Used over SpaceWire (SpW) –Minimize packet overhead –Be generic in nature Developed to use Protocol ID (PID) standardized by ECSS-E-50-11 –Permanent Protocol ID request pending Developed by Geostationary Environmental Satellite (GOES) -R series project –Protocol developed to meet project data loss requirement

3. 32006 MAPLD International ConferenceSpaceWire 101 Seminar RDDP Modes Nominal Mode –Reliable Delivery – Acknowledge (ACK) every good packet Urgent Message Mode –No ACKS & No Retransmits, fire and forget

4. 42006 MAPLD International ConferenceSpaceWire 101 Seminar How It Works The protocol provides multiple virtual channels multiplexed over a single SpaceWire connection. Each virtual channel is independent of all other channels. Channels should have allocated buffer space, and parameters set for each channel. After ACK timeout, selective retransmit can occur.

5. 52006 MAPLD International ConferenceSpaceWire 101 Seminar XMTR establishes link by sending a RESET to the receiver –RCVR never sends RESET, XMTR never receives RESET XMTR may send up to Window Size packets ahead of last ACK After ACK timeout, retransmit up to Max Retries number of times After Max Retries is exhausted, notify host and quit. Host may issue RESET How It Works Transmitter

6. 62006 MAPLD International ConferenceSpaceWire 101 Seminar Receiver sends ACK for every error free packet –No EOP, no CRC error, valid header Receiver orders Reliable Delivery packets and eliminates duplicates Receiver does not close or RESET a channel Receiver may wait forever to receive opening RESET or next valid packet How It Works Receiver

7. 72006 MAPLD International ConferenceSpaceWire 101 Seminar RDDP Features 2-Dword header. Programmable parameters – sliding window size, timeouts, and retries. 8 Bit CRC.

8. 82006 MAPLD International ConferenceSpaceWire 101 Seminar SpaceWire Protocol Identifier* Logical Address Protocol IDRest of PacketEOP Logical Address Protocol IDRest of PacketEOP Path Address Logical Address and Protocol ID Path Address and Protocol ID * Slide from SpaceWire RMAP Protocol, Steve Parkes, University of Dundee

9. 92006 MAPLD International ConferenceSpaceWire 101 Seminar RDDP Packet Format Destination Logical AddressProtocol IDSource Logical AddressPacket Control** Packet Length (MSB)Packet Length (LSB)Channel NumberSequence Number Data Data*GRDDP Packet CRCEOP First byte transmitted Last byte transmitted * Data length is 0 to 6553 bytes ** Bits in Packet Control – User Defined / Packet Type: 0 0 0 0 Packet (expect ACK) 0 0 0 1 Acknowledgement (ACK) 0 0 1 0 Reset Command 0 0 1 1 Urgent Message (No ACK) User definedPacket Type 4 bits MSB LSB MSBLSB

10. 102006 MAPLD International ConferenceSpaceWire 101 Seminar RDDP ABI Data Model GRDDP HeaderCCSDS Source Packet 1CCSDS Source Packet 2 GRDDP Packet CRCEOP CCSDS Source Packet 3 CCSDS Source Packet 4CCSDS Source Packet 5CCSDS Source Packet 6CCSDS Source Packet 7 CCSDS Source Packet 8 Imager Science Data

11. 112006 MAPLD International ConferenceSpaceWire 101 Seminar Definitions (1) Logical Address - defined in the SpaceWire standard –Identifies the destination of the packet Range of 32 to 255 decimal Used by SpW router look-up table to associate an output port number –If destination is unknown than default value of 254 used May or may not be used for routing purposes Node may reject or accept packet with logical address 254 Path Address –Identifies PATH to destination May be physical or logical (range is 1..253) Specifies the SLA to route packet Will NEED to be deleted by intermediate routers so that only destination logical address remains when delivered to protocol destination Destination Logical Address –Destination virtual channel identifier Source Logical Address –Logical address from which packet was transmitted –May be used to send back acknowledgements

12. 122006 MAPLD International ConferenceSpaceWire 101 Seminar Definitions (2) Protocol Identifier (ID) –Specifies the packet format –PID requested for RDDP Currently in experimental range Packet Control –Packet Type Packet to be acknowledged Packet not to be acknowledged –Urgent message Acknowledgement Packet Reset Command –User defined For example: could be a sub-protocol ID used to identify different packet cargo types using RDDP Packet Length –2 bytes –Used to indicate packet cargo length (bytes) –May be from 0 to 65535 bytes

13. 132006 MAPLD International ConferenceSpaceWire 101 Seminar Definitions (3) Channel Number –1 byte –Allows sub-addressing within a source destination pair (1553) Sequence Number –1 byte –Used to associate a packet and acknowledgement pair Current protocol has a fixed range of 0 to 255 Data –0 to 65535 bytes –Data to be transferred using RDDP CRC –8 bit CRC Same as ATM (HEC) –Used to confirm that header and data were received correctly

14. 142006 MAPLD International ConferenceSpaceWire 101 Seminar Sliding Window The RDDP Utilizes Selective Retransmit The sliding window allows users to improve bandwidth efficiency. -- Gets around send and wait for ACK. -- Window size, timeouts, and number of retries can be tuned for maximum efficiency --- Window size should be half sequence number. Allows reordering packets if received out of sequence. Detects duplicate packets.

15. 152006 MAPLD International ConferenceSpaceWire 101 Seminar Nominal Operation No Errors – Fast ACKs SourceDestination Packet n+1 ACK n+1 Packet n+2 ACK n+2 Packet n+8 ACK n+8.... Tx Window advances 1 (may send next new packet) Tx Window advances 1 (may send next new packet).... Tx Window advances 1 (may send next new packet)

16. 162006 MAPLD International ConferenceSpaceWire 101 Seminar Nominal Operation No Errors – Burst Packets & or Slow ACKs SourceDestination Packet 1 ACK 1 Packet 2 ACK 2 Tx Window advances 1 Packet 3 Packet 4 ACK 3 ACK 4 Transmitter can send up to window size number of packets before having to wait to receive an ACK

17. 172006 MAPLD International ConferenceSpaceWire 101 Seminar Nominal Operation – ACK Error, Ex. 1 Source Destination Packet 1 ACK 1 Time-Out Packet 2 ACK 2 ACK 3 Packet 3 ACK 4 Packet 4 Resend Packet 1 Next New Packet Ex. window size 4 Tx window may only be advanced by number of contiguous ACKed packet received from start of Tx window Tx window must wait to send packets until ACK 1 received ACK 1 Tx Window advances 4 (may now send 4 new packets) Rx Window discards duplicate packet 1 The next packet for window entry #1 will be Sequence #5 with new data packet content

18. 182006 MAPLD International ConferenceSpaceWire 101 Seminar GOES-R Reliable Data Delivery Protocol - Platforms The GOES-R RDDP is now running on 3 hardware configurations Development and testing has been SWTS to SWTS and SWTS to BAE ASIC –FPGA based SpaceWire Test Set (SWTS) NASA SpW core Windows PCI workstation –BAE Systems SpW ASIC integrated onto commercial PC board NASA SpW core PCI Windows workstation –BAE Systems SpW ASIC integrated onto flight board (ITT/ABI Rev A.) cPCI form factor Uses RAD750 over cPCI VxWorks

19. 192006 MAPLD International ConferenceSpaceWire 101 Seminar GOES-R Reliable Data Delivery Protocol - SWTS The SWTS is a COTS card with FPGA image modified for GOES-R.

20. 202006 MAPLD International ConferenceSpaceWire 101 Seminar SPACEWIRE ASIC Block Diagram BAE Systems OCB Connection Medium EMC 64 OCB Master 64 OCB Slave SRAM 16K bytes 64 OCB Slave PID’s MISC OCB Slave 32 UART 32 OCB Slave PCI 2.2 64 OCB Master OCB Slave PCI 9 HP masters 6 HP slaves 1 LP master 6 LP slaves 64 OCB Master 32 OCB Slave 64 DMA OCB Master Reused New or Modified Clocks/Reset CAT 32 PLL OCB Slave PCI 2.2 64 OCB Master OCB Slave PCI Spacewire Router and Links Spacewire I/F JTAG 32 OCB Master JTAG Slave (JTAG) SRAM 16K bytes 64 OCB Slave 64 OCB Master 32 OCB Slave 64 OCB Master RIF 64 OCB Master 32 OCB Slave 64 OCB Master RIF FIFO MCTL 64 OCB Slave External Memory I/F SRAM SDRAM EEPROM

21. 212006 MAPLD International ConferenceSpaceWire 101 Seminar GOES-R Reliable Data Delivery Protocol – ASIC Test Card

22. 222006 MAPLD International ConferenceSpaceWire 101 Seminar GOES-R Reliable Data Delivery Protocol – ITT/ABI cPCI Card The ITT/ABI BAE ASIC proto flight with RAD750 and connected to SWTS workstations.

23. 232006 MAPLD International ConferenceSpaceWire 101 Seminar RDDP Team Bill Anderson – GOES-R C&DH Lead Engineer Craig Bearer – GOES-R C&DH Engineer – Software Marco Figueiredo – GOES-R Senior Hardware Engineer Eric Lynum – GOES-R Electrical Design Engineer Dan May – GOES-R Test Engineer Glenn Rakow – GSFC SpaceWire Consultant Jeffrey A. Kronenwetter– GOES-R ABI System Engineer Alexander Krimchansky – GOES-R Systems Manager