Lantronix DSTni-EX manual USB Background, USB Interrupt, USB Core, Theory of Operation

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Theory of Operation

USB Background

USB is a serial bus operating at 12 Mb/s. USB provides an expandable, hot-pluggable Plug- and-Play serial interface that ensures a standard, low-cost socket for adding external peripheral devices.

USB allows the connection of up to 127 devices. Devices suitable for USB range from simple input devices such as keyboards, mice, and joysticks, to advanced devices such as printers, scanners, storage devices, modems, and video-conferencing cameras.

Version 1.1 of the USB specification provides for peripheral speeds of up to 1.5 Mbps for low- speed devices and up to 12 Mbps for full-speed devices.

USB Interrupt

The DSTni USB interrupt is located at base input/output (I/O) of 9800h. It is logically ORed with external interrupt 3.

USB Core

The USB core has three functional blocks.

Serial Interface Engine (SIE)

Microprocessor Interface

Digital Phase-Locked Loop Logic

Serial Interface Engine

The USB Serial Interface Engine (USB SIE) has two major sections: Tx Logic and Rx Logic.

Tx Logic formats and transmits data packets that the microprocessor builds in memory. These packets are converted from a parallel-to-serial data stream. Tx Logic performs all the necessary USB data formatting, including:

NRZI encoding Bit-stuff

Cyclic Redundancy Check (CRC) computation Addition of SYNC field and EOP

The Rx Logic receives USB data and stores the packets in memory so the microprocessor can process them. Serial USB data converts to a byte-wide parallel data stream and is stored in system memory. The receive logic:

Decodes an NRZ USB serial data stream Performs bit-stuff removal

Performs CRC check, PID check, and other USB protocol-layer checks

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Contents Section Five DSTni-EX User GuidePage Master Distributor Copyright & TrademarkLantronix Technical SupportWarranty 3 I2C Controller Contents1 About This User Guide 2 SPI Controller5 CAN Controllers List of TablesTable 3-17. Clock Control Register List of Figures 1 About This User Guide Notes Notes are information requiring attention Intended AudienceConventions Navigating OnlineOrganization DSTni SPI Controller 2 SPI ControllerTheory of Operation SPI BackgroundTable 2-1. SPI Controller Register Summary SPI Controller Register SummaryTable 2-2. SPIDATA Register SPI Controller Register DefinitionsSPIDATA Register RESETWire-O CTL RegisterInterrupt Request Enable Phase SelectInterrupt Request SPISTAT RegisterTable 2-6. SPISTAT Register Table 2-7. SPISTAT Register DefinitionsTable 2-8. SPISSEL Register SPISSEL RegisterTable 2-10. BCNT Bit Settings SelectO SignalTable 2-12. DVDCNTRLO Register Definitions DVDCNTRLO RegisterDVDCNTRHI Table 2-11. DVDCNTRLO Register3 I2C Controller FeaturesBlock Diagram I2C BackgroundFigure 3-1. DSTni I2C Controller Block Diagram I2C Controller Operating ModesMaster Transmit Mode Microprocessor Response Table 3-1. Master Transmit Status CodesCode I2C StateTable 3-2. Codes After Servicing Interrupts Master Transmit Servicing the InterruptMaster Receive Mode Transmitting Each Data ByteTable 3-3. Status Codes After Each Data Byte Transmits All Bytes Transmit CompletelyTable 3-4. Master Receive Status Codes Table 3-5. Codes After Servicing Interrupt Master Receive Receiving Each Data Byte Table 3-6. Codes After Receiving Each Data ByteSlave Transmit Mode Slave Receive Mode Bus Arbitration Bus Clock ConsiderationsBus Clock Speed Clock SynchronizationTable 3-7. I 2C Controller Register Summary Programmer’s ReferenceI2C Controller Register Summary Resetting the I2C ControllerTable 3-8. Slave Address Register I2C Controller Register DefinitionsSlave Address Register General Call Address EnableTable 3-10. Data Register Data RegisterExtended Slave Address Control RegisterTable 3-12. Control Register Table 3-13. Control Register DefinitionsTable 3-14. Status Register Status RegisterTable 3-15. Status Register Definitions Table 3-16. Status CodesStatus Code Clock Control Register Table 3-17. Clock Control RegisterTable 3-18. Clock Control Register Definitions Table 3-22. Software Reset Register Definitions Software Reset RegisterExtended Slave Address Register Table 3-21. Software Reset Register4 USB Controller Serial Interface Engine USB BackgroundUSB Interrupt USB CoreBuffer Descriptor Table USB Hardware/Software InterfaceDigital Phase Lock Loop Logic Microprocessor InterfaceRx vs. Tx as a Target Device or Host Figure 4-1. Buffer Descriptor TableTable 4-3. 16-Bit USB Address Definitions Table 4-1. USB Data DirectionAddressing BDT Entries Table 4-2. 16-Bit USB AddressTable 4-5. USB Buffer Descriptor Format Table 4-4. BDT Data Used by USB Controller and MicroprocessorUSB Controller Determines… Microprocessor Determines…USB Ownership Table 4-6. USB Buffer Descriptor Format DefinitionsBD Owner DATA0/1 Transmit or ReceiveFigure 4-2. USB Token Transaction USB TransactionUSB Register Summary Table 4-7. USB Register SummaryDedicated to host mode Table 4-9. 16- Interrupt Status Register Definitions USB Register DefinitionsInterrupt Status Register Table 4-8. Interrupt Status RegisterUSB Reset Enable/Disable USBRST InterruptSleep Timer Error ConditionError Register Table 4-10. Error Interrupt Status RegisterTable 4-11. 16- Error Interrupt Status Register Definitions PID check field failed Error interrupt with two functionsData Field Received Not 8 Bits CRC16 FailureTable 4-13. Status Register Definitions Live USB Differential Receiver JSTATE SignalLive USB Single Ended Zero Signal Table 4-12. Status RegisterBDT PDD Reset USB Reset SignalHost Mode Enable valid for host mode only Resume SignalingAddress Register Table 4-14. Address RegisterTable 4-15. 16- Address Register Definitions Frame Number Frame Number RegistersTable 4-16. Frame Number Register Table 4-17. Frame Number Register DefinitionsToken Register Table 4-20. Valid PID Tokens Endpoint for Token CommandTable 4-18. Token Register Table 4-19. Token Register DefinitionsTable 4-22. Endpoint Control Register Definitions Endpoint Control RegistersEndpoint Enable Table 4-21. Endpoint Control RegistersTable 4-23. Endpoint Control Register Definitions Host Mode OperationFigure 3. Enable Host Mode and Configure a Target Device Sample Host Mode OperationsFigure 4. Full-Speed Bulk Data Transfers to a Target Device Figure 4-5. Pull-up/Pull-down USB USB Pull-up/Pull-down ResistorsClock CLK USB Interface SignalsUSB Output Enable HOST Mode Enable5 CAN Controllers Arbitration and Error Checking CANBUS BackgroundData Exchanges and Communication Table 5-1. Bit Rates for Different Cable Lengths CANBUS Speed and LengthRegister CAN Register SummariesRegister Summary Hex OffsetRegister Table 5-4. Detailed CAN Register Map Detailed CAN Register MapHex Offset Acceptance Filter Enable RegisterRegister Sending a Message CAN Register DefinitionsTX Message Registers Figure 5-1. TX Message RoutingTable 5-7. TxMessage0Data Tx Message RegistersTable 5-5. TxMessage0ID28 Table 5-6. TxMessage0ID12Message Data Table 5-12. TxMessage0Ctrl FlagsTable 5-13. TxMessage0 Register Definitions Message Identifier for Both Standard and Extended MessagesFigure 5-2. RX Message Routing RX Message RegistersTable 5-16. RxMessageID12 Rx Message RegistersTable 5-14. RxMessageID28 Table 5-15. Rx Message ID28 Register DefinitionsTable 5-23. Rx Message Data 23 Register Definitions Table 5-20. Rx Message DataTable 5-21. Rx Message Data 39 Register Definitions Table 5-22. Rx Message DataTable 5-29. Rx Message Msg Flags Register Definitions Table 5-26. RxMessage RTRTable 5-27. Rx Message RTR Register Definitions Table 5-28. Rx Message Msg FlagsTable 5-32. Error Status Error Count and Status RegistersTable 5-30. Tx/Rx Error Count Table 5-31. Tx\Rx Error Count Register Definitionstxlevel10 Table 5-34. Tx/Rx Message Level RegisterTable 5-35. Tx/Rx Message Level Register Definitions rxlevel10Format Error Interrupt FlagsNote The reset value of this register’s bits is indeterminate CRC ErrorBus Off State − int2n group error interrupts Interrupt Enable RegistersTable 5-38. Interrupt Enable Registers Table 5-39. Interrupt Enable Register DefinitionsOverload Condition − int3n group diagnostic interrupts CAN Operating ModeTable 5-40. Interrupt Enable Registers Table 5-41. Interrupt Enable Register DefinitionsTable 5-42. Bit Rate Divisor Register CAN Configuration RegistersConfiguration Bit Rate Figure 5-3. CAN Operating ModeCfgsjw Table 5-44. Configuration RegisterTable 5-45. Configuration Register Definitions Overwrite Last Messagetime quanta TQ Bit Timetseg1 + tseg2 +Table 5-48. Acceptance Mask 0 Register Acceptance Filter and Acceptance Code MaskTable 5-46. Acceptance Filter Enable Register Table 5-47. Acceptance Filter Enable Register DefinitionsD5556 Table 5-50. Acceptance Mask Register IDTable 5-51. Acceptance Mask Register ID12 Definitions Table 5-52. Acceptance Mask Register DataTable 5-57. Acceptance Mask Register ID12 Definitions Table 5-54. Acceptance Code RegisterTable 5-55. Acceptance Code Register Definitions Table 5-56. Acceptance Mask Register ID12Table 5-61. Arbitration Lost Capture Register Definitions CANbus AnalysisArbitration Lost Capture Register Table 5-60. Arbitration Lost Capture RegisterErrorcode Error Capture RegisterTable 5-62. Error Capture Register Table 5-63. Error Capture Register DefinitionsStuff Bit Inserted Table 5-65. Error Capture Register DefinitionsFrame Reference Register Table 5-64. Frame Reference RegisterFigure 5-5. CAN Bus Interface CAN Bus InterfaceInterface Connections Figure 5-6. CAN Connector+24V Figure 5-7. Power for CAN+5CAN GNDCAN0.01uf Figure 5-8. CAN Transceiver and Isolation Circuits