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May 16, 2000

May 16, 2000. 2. Data Transfer

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May 16, 2000

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    1. May 16, 2000 1

    2. May 16, 2000 2 Data Transfer & Framework John Garney Hub Working Group Chair Intel Corporation

    3. May 16, 2000 3 High Speed Additions Data Transfer Microframes Maximum Packet Sizes Additions to Chapter 5 Framework Other Speed Descriptors Test Mode Feature Additions to Chapter 9

    4. May 16, 2000 4 HS Data Transfer Changes - High Speed Microframes 125us HS Microframe Less buffering required for HS devices than for 1ms frame No new transaction for “microframe SOF”, use SOF SOF on HS occurs 8x more frequently HS Devices can derive microframe number if required

    5. May 16, 2000 5 HS Data Transfer Changes - Maximum Data Payloads wMaxPacketSize field in endpoint descriptor High Speed Devices, no changes for FS/LS Control: 64 bytes Allows FS: 8,16,32,64, LS:8 Bulk: 512 bytes Allows FS: 8,16,32,64, LS: not allowed Increases high speed bus efficiency Reduces complexity in host SW & HW

    6. May 16, 2000 6 HS Data Transfer Changes - Maximum Data Payloads Interrupt: <=3072 bytes per 2bInterval-1 microframes Allows FS: <=64 bytes per 1…255 ms, LS:<=8 per 8…255ms Isochronous: <=3072 bytes per 2bInterval-1 microframes Allows FS: <=1023 bytes per 2bInterval-1 ms, LS: not allowed If >1024 bytes, done with multiple normal transactions Each data payload is <=1024 bytes (up to 3x per microframe) Data payloads are “max sized”, residual in last Allows HS periodic endpoint up to 192Mb/s

    7. May 16, 2000 7 High Bandwidth Endpoint Maximum payload 3x 1024 bytes per microframe At most 3 transactions: e.g. token, data & handshake packets Each transaction data payload at most 1024 bytes Interrupt IN/OUT Uses normal DATA0, DATA1 data packet PID toggling and retries Isochronous IN/OUT Uses data sequencing with DATA0, DATA1, DATA2, MDATA PIDs

    8. May 16, 2000 8 High BW Interrupt IN/OUT At most 3 transactions attempts per microframe Error reduces data per microframe No additional retries in microframe Continuous data toggling on good transactions Continues across microframes Unless restarted by endpoint configuration change

    9. May 16, 2000 9 High BW Isochronous OUT Last data packet PID tells device # of transactions DATA0=1, DATA1=2, DATA2=3 1st/2nd data packets use MDATA data packet PID Sequence “restarts” each microframe Device can detect errors Never retried, device-specific recovery

    10. May 16, 2000 10 High BW Isochronous IN First data packet PID tells host # of transactions DATA0=1, DATA1=2, DATA2=3 2nd/3rd data packets use “decreasing” data packet PIDs Sequence “restarts” each microframe Host can detect errors/timeouts Never retried, aborts remaining transactions in uframe

    11. May 16, 2000 11 HS Framework Changes - Other_Speed Descriptors HS capable device must enumerate in FS also Must not confuse “old” FS software Normal descriptors returned for current speed HS capable devices can report other_speed choice HS info when in FS port Allows wizard to assist end user FS info when in HS port “What happens if in USB 1.1 port?” Device_Qualifier descriptor Other_Speed_Configuration descriptor

    12. May 16, 2000 12 HS Framework Changes - Device_Qualifier Descriptor Device_Qualifier Descriptor reports: Version, class/subclass/protocol for other speed Default endpoint wMaxPacketSize for other speed Reports # of configurations for other speed

    13. May 16, 2000 13 HS Framework Changes - Other_Speed_Configuration Descriptor Other_Speed_Configuration Descriptor reports: A speed dependent configuration for the other speed

    14. May 16, 2000 14 HS Framework Changes - Enhanced Endpoint Descriptor Endpoint Descriptor No data structure changes, only encoding/ interpretation changes Larger HS payloads (values) High BW has size = (multiplier X max_data_size) For HS device, bInterval periods are in microframes (125us) For full/low speed device, bInterval is in frames (1ms) HS devices: bInterval value is N, endpoint period is 2N-1 “Periodic” Isochronous Allows slower (2N-1 microframes) isochronous rates

    15. May 16, 2000 15 HS Framework Changes - High Speed Test Mode Request Test Mode Request and Parameters Allows standardized testing of HS transceivers Upstream ports of all HS devices Downstream ports of Hubs (also host controller) Test Modes (as defined in chapter 7) Test_J, Test_K, Test_SE0_NAK, Test_Packet, Test_Force_Enable Enter via a Set_Feature request Exit via device power cycle or hub reset

    16. May 16, 2000 16 Data Transfer & Framework Additions Summary 125us Microframe Reduces device buffering Fewer Maximum Packet Size Choices Simpler host Larger Packet Sizes (Bulk, Int., Isoch.) Improved bus efficiency, higher device throughput Report High- and Full-Speed Configurations Dual Speed devices supported Required HS Test Mode Improved Compliance and interoperability

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