May 16, 20001

2 Data Transfer & Framework John Garney Hub Working Group Chair Intel Corporation John Garney Hub Working Group Chair Intel Corporation

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

May 16, HS Data Transfer Changes - High Speed Microframes w 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 Full / Low Speed Frame Size (1ms) High Speed Micro-Frames (125us) 1ms1ms Classic USB Frame Ticks Full Speed Isochronous Data Payload USB 2.0 Micro-Frame Ticks (1/8 th Classic Frame) High Speed Isochronous Data Payload

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

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

May 16, High Bandwidth Endpoint w 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 w Interrupt IN/OUT – Uses normal DATA0, DATA1 data packet PID toggling and retries w Isochronous IN/OUT – Uses data sequencing with DATA0, DATA1, DATA2, MDATA PIDs TokenToken 125us Microframe DATAxDATAxTokenTokenDATAxDATAxTokenTokenDATAxDATAx Transaction #1 Transaction #2 Transaction #3 HHHHHH

May 16, High BW Interrupt IN/OUT w At most 3 transactions attempts per microframe w Error reduces data per microframe – No additional retries in microframe w Continuous data toggling on good transactions – Continues across microframes – Unless restarted by endpoint configuration change DATA0DATA0DATA1DATA1 125us Microframe DATA0DATA0DATA1DATA1 X DATA1DATA1TTTTTTTTTTHHHHHHHH

May 16, High BW Isochronous OUT w Last data packet PID tells device # of transactions – DATA0=1, DATA1=2, DATA2=3 w 1st/2nd data packets use MDATA data packet PID w Sequence “restarts” each microframe w Device can detect errors – Never retried, device-specific recovery DATA0DATA0 1 transaction, <1024 bytes: TT MDATAMDATADATA1DATA1 2 transactions, bytes ea.: TTTT MDATAMDATAMDATAMDATADATA2DATA2 3 transactions, bytes ea.: TTTTTT

May 16, High BW Isochronous IN w First data packet PID tells host # of transactions – DATA0=1, DATA1=2, DATA2=3 w 2nd/3rd data packets use “decreasing” data packet PIDs w Sequence “restarts” each microframe w Host can detect errors/timeouts – Never retried, aborts remaining transactions in uframe DATA0DATA0 1 transaction, <1024 bytes: TT DATA1DATA1DATA0DATA0 2 transactions, bytes ea.: TTTT DATA2DATA2DATA1DATA1DATA0DATA0 3 transactions, bytes ea.: TTTTTT

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

May 16, Offset Field Description bLength bDescriptorType bcdUSB bDeviceClass bDeviceSubClass bDeviceProtocol wMaxPacketSize0 bNumConfigurations bReserved Size of descriptor Device_Qualifier Type USB Spec version number (e.g for V2.0.0 ) Class Code SubClass Code Protocol Code Maximum packet size for other speed Number of Other_Speed_Configurations Reserved for future use, must be zero HS Framework Changes - Device_Qualifier Descriptor w Device_Qualifier Descriptor reports: – Version, class/subclass/protocol for other speed – Default endpoint wMaxPacketSize for other speed – Reports # of configurations for other speed

May 16, Offset Field Description bLength BdescriptorType wTotalLength bNumInterfaces bConfigurationValue iConfiguration bmAttributes bMaxPower Size of descriptor Other_Speed_Configuration Type Total length of data returned … Number of interfaces supported by this speed configuration. Value to use to select configuration… Index of string descriptor… Same as Configuration descriptor HS Framework Changes - Other_Speed_Configuration Descriptor w Other_Speed_Configuration Descriptor reports: – A speed dependent configuration for the other speed

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

May 16, HS Framework Changes - High Speed Test Mode Request w Test Mode Request and Parameters – Allows standardized testing of HS transceivers u Upstream ports of all HS devices u Downstream ports of Hubs (also host controller) – Test Modes (as defined in chapter 7) u 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

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