Lantronix DSTni-EX manual Theory of Operation, SPI Background, DSTni SPI Controller

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2: SPI Controller

2: SPI Controller

This chapter describes the DSTni Serial Peripheral Interface (SPI) controller. Topics include:

Theory of Operation on page 4

SPI Controller Register Summary on page 5 SPI Controller Register Definitions on page 6

Theory of Operation

SPI Background

SPI is a high-speed synchronous serial input/output (I/O) port that allows a serial bit stream of programmed length (one to eight bits) to be shifted into and out of the device at a programmable bit-transfer rate.

SPI is an industry-standard communications interface that does not have specifications or a standards organizing group. As a result, there are no licensing requirements. Because of its simplicity, SPI is commonly used in embedded systems. Many semiconductor manufacturers sell a variety of sensor, conversion, and control devices that use SPI.

DSTni SPI Controller

The DSTni SPI controller is located at base I/O address B800h. It shares an interrupt with the I2C controller and connects to interrupt 2. The SPI controller is enabled using the DSTni Configuration register. If set to 1, the SPI controller is enabled on serial port 3. This bit can reset to 1 with an external pull-up resistor. Normally it resets to 0 on reset or power-up.

The SPI bus is a 3-wire bus serial bus that links a serial shift register between a master device and a slave device. This design supports both master and slave operations. Typically, master and slave devices have an 8-bit shift register, for a combined register of 16 bits. During an SPI transfer, the master and slave shift registers by eight bits and exchange their 8-bit register values, starting with the most-significant bit.

The SPI interface is software configurable. The clock polarity, clock phase, SLVSEL polarity, clock frequency in master mode, and number of bits to be transferred are all software programmable. SPI supports multiple slaves on a single 3-wire bus by using separate Slave Select signals to enable the desired slave. Multiple masters are also fully supported and some support is provided for detecting collisions when multiple masters attempt to transfer at the same time.

A Wired-OR mode is provided which allows multiple masters to collide on the bus without risk of damage. In this mode, an external pull-up resistor is required on the Master Out Slave In (MOSI) ) and Master In Slave Out (MISO) pins. The wired-OR mode also allows the SPI bus to operate as a 2-wire bus by connecting the MOSI and MISO pins to form a single bi-directional data pin. Generally, pull-ups are recommended on all of the external SPI signals to ensure they are held in a valid state, even when the SPI interface is disabled. For some device connections, the ALT mode bit will swap the TX and RX pins.

The SPI controller has an enhanced mode called AUTODRV. This mode is valid in master mode. In this mode, the SLVSEL pin is driven active when data is written to the data register. After the last bit of data is shifted out, the SLVSEL goes inactive and an interrupt is generated. The INVCS bit can generate either a positive or negative true SLVSEL pin.

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Contents DSTni-EX User Guide Section FivePage Copyright & Trademark LantronixTechnical Support Master DistributorWarranty Contents 1 About This User Guide2 SPI Controller 3 I2C ControllerList of Tables 5 CAN ControllersTable 3-17. Clock Control Register List of Figures 1 About This User Guide Intended Audience ConventionsNavigating Online Notes Notes are information requiring attentionOrganization 2 SPI Controller Theory of OperationSPI Background DSTni SPI ControllerSPI Controller Register Summary Table 2-1. SPI Controller Register SummarySPI Controller Register Definitions SPIDATA RegisterRESET Table 2-2. SPIDATA RegisterCTL Register Interrupt Request EnablePhase Select Wire-OSPISTAT Register Table 2-6. SPISTAT RegisterTable 2-7. SPISTAT Register Definitions Interrupt RequestSPISSEL Register Table 2-10. BCNT Bit SettingsSelectO Signal Table 2-8. SPISSEL RegisterDVDCNTRLO Register DVDCNTRHITable 2-11. DVDCNTRLO Register Table 2-12. DVDCNTRLO Register DefinitionsFeatures 3 I2C ControllerBlock Diagram I2C BackgroundFigure 3-1. DSTni I2C Controller Block Diagram I2C Controller Operating ModesMaster Transmit Mode Table 3-1. Master Transmit Status Codes CodeI2C State Microprocessor ResponseServicing the Interrupt Table 3-2. Codes After Servicing Interrupts Master TransmitTransmitting Each Data Byte Table 3-3. Status Codes After Each Data Byte TransmitsAll Bytes Transmit Completely Master Receive ModeTable 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 Clock Considerations Bus Clock SpeedClock Synchronization Bus ArbitrationProgrammer’s Reference I2C Controller Register SummaryResetting the I2C Controller Table 3-7. I 2C Controller Register SummaryI2C Controller Register Definitions Slave Address RegisterGeneral Call Address Enable Table 3-8. Slave Address RegisterData Register Table 3-10. Data RegisterControl Register Table 3-12. Control RegisterTable 3-13. Control Register Definitions Extended Slave AddressStatus Register Table 3-14. 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 Software Reset Register Extended Slave Address RegisterTable 3-21. Software Reset Register Table 3-22. Software Reset Register Definitions4 USB Controller USB Background USB InterruptUSB Core Serial Interface EngineUSB Hardware/Software Interface Digital Phase Lock Loop LogicMicroprocessor Interface Buffer Descriptor TableFigure 4-1. Buffer Descriptor Table Rx vs. Tx as a Target Device or HostTable 4-1. USB Data Direction Addressing BDT EntriesTable 4-2. 16-Bit USB Address Table 4-3. 16-Bit USB Address DefinitionsTable 4-4. BDT Data Used by USB Controller and Microprocessor USB Controller Determines…Microprocessor Determines… Table 4-5. USB Buffer Descriptor FormatTable 4-6. USB Buffer Descriptor Format Definitions BD OwnerDATA0/1 Transmit or Receive USB OwnershipUSB Transaction Figure 4-2. USB Token TransactionUSB Register Summary Table 4-7. USB Register SummaryDedicated to host mode USB Register Definitions Interrupt Status RegisterTable 4-8. Interrupt Status Register Table 4-9. 16- Interrupt Status Register DefinitionsEnable/Disable USBRST Interrupt Sleep TimerError Condition USB ResetError Register Table 4-10. Error Interrupt Status RegisterTable 4-11. 16- Error Interrupt Status Register Definitions Error interrupt with two functions Data Field Received Not 8 BitsCRC16 Failure PID check field failedLive USB Differential Receiver JSTATE Signal Live USB Single Ended Zero SignalTable 4-12. Status Register Table 4-13. Status Register DefinitionsUSB Reset Signal Host Mode Enable valid for host mode onlyResume Signaling BDT PDD ResetAddress Register Table 4-14. Address RegisterTable 4-15. 16- Address Register Definitions Frame Number Registers Table 4-16. Frame Number RegisterTable 4-17. Frame Number Register Definitions Frame NumberToken Register Endpoint for Token Command Table 4-18. Token RegisterTable 4-19. Token Register Definitions Table 4-20. Valid PID TokensEndpoint Control Registers Endpoint EnableTable 4-21. Endpoint Control Registers Table 4-22. Endpoint Control Register DefinitionsHost Mode Operation Table 4-23. Endpoint Control Register DefinitionsSample Host Mode Operations Figure 3. Enable Host Mode and Configure a Target DeviceFigure 4. Full-Speed Bulk Data Transfers to a Target Device USB Pull-up/Pull-down Resistors Figure 4-5. Pull-up/Pull-down USBUSB Interface Signals USB Output EnableHOST Mode Enable Clock CLK5 CAN Controllers Arbitration and Error Checking CANBUS BackgroundData Exchanges and Communication CANBUS Speed and Length Table 5-1. Bit Rates for Different Cable LengthsCAN Register Summaries Register SummaryHex Offset RegisterHex Offset Detailed CAN Register Map Table 5-4. Detailed CAN Register MapAcceptance Filter Enable Register Hex OffsetRegister CAN Register Definitions TX Message RegistersFigure 5-1. TX Message Routing Sending a MessageTx Message Registers Table 5-5. TxMessage0ID28Table 5-6. TxMessage0ID12 Table 5-7. TxMessage0DataTable 5-12. TxMessage0Ctrl Flags Table 5-13. TxMessage0 Register DefinitionsMessage Identifier for Both Standard and Extended Messages Message DataRX Message Registers Figure 5-2. RX Message RoutingRx Message Registers Table 5-14. RxMessageID28Table 5-15. Rx Message ID28 Register Definitions Table 5-16. RxMessageID12Table 5-20. Rx Message Data Table 5-21. Rx Message Data 39 Register DefinitionsTable 5-22. Rx Message Data Table 5-23. Rx Message Data 23 Register DefinitionsTable 5-26. RxMessage RTR Table 5-27. Rx Message RTR Register DefinitionsTable 5-28. Rx Message Msg Flags Table 5-29. Rx Message Msg Flags Register DefinitionsError Count and Status Registers Table 5-30. Tx/Rx Error CountTable 5-31. Tx\Rx Error Count Register Definitions Table 5-32. Error StatusTable 5-34. Tx/Rx Message Level Register Table 5-35. Tx/Rx Message Level Register Definitionsrxlevel10 txlevel10Interrupt Flags Note The reset value of this register’s bits is indeterminateCRC Error Format ErrorInterrupt Enable Registers Table 5-38. Interrupt Enable RegistersTable 5-39. Interrupt Enable Register Definitions Bus Off State − int2n group error interruptsCAN Operating Mode Table 5-40. Interrupt Enable RegistersTable 5-41. Interrupt Enable Register Definitions Overload Condition − int3n group diagnostic interruptsCAN Configuration Registers Configuration Bit RateFigure 5-3. CAN Operating Mode Table 5-42. Bit Rate Divisor RegisterTable 5-44. Configuration Register Table 5-45. Configuration Register DefinitionsOverwrite Last Message CfgsjwBit Time tseg1 +tseg2 + time quanta TQAcceptance Filter and Acceptance Code Mask Table 5-46. Acceptance Filter Enable RegisterTable 5-47. Acceptance Filter Enable Register Definitions Table 5-48. Acceptance Mask 0 RegisterTable 5-50. Acceptance Mask Register ID Table 5-51. Acceptance Mask Register ID12 DefinitionsTable 5-52. Acceptance Mask Register Data D5556Table 5-54. Acceptance Code Register Table 5-55. Acceptance Code Register DefinitionsTable 5-56. Acceptance Mask Register ID12 Table 5-57. Acceptance Mask Register ID12 DefinitionsCANbus Analysis Arbitration Lost Capture RegisterTable 5-60. Arbitration Lost Capture Register Table 5-61. Arbitration Lost Capture Register DefinitionsError Capture Register Table 5-62. Error Capture RegisterTable 5-63. Error Capture Register Definitions ErrorcodeTable 5-65. Error Capture Register Definitions Frame Reference RegisterTable 5-64. Frame Reference Register Stuff Bit InsertedCAN Bus Interface Interface ConnectionsFigure 5-6. CAN Connector Figure 5-5. CAN Bus InterfaceFigure 5-7. Power for CAN +5CANGNDCAN +24VFigure 5-8. CAN Transceiver and Isolation Circuits 0.01uf
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