SWCU193A April   2023  – August 2024 CC2340R2 , CC2340R5 , CC2340R5-Q1

 

  1.   1
  2.   Read This First
    1.     About This Manual
    2.     Devices
    3.     Register, Field, and Bit Calls
    4.     Related Documentation
    5.     Trademarks
  3. 1 Architectural Overview
    1. 1.1  Target Applications
    2. 1.2  Introduction
    3. 1.3  Arm Cortex M0+
      1. 1.3.1 Processor Core
      2. 1.3.2 SysTick Timer
      3. 1.3.3 Nested Vectored Interrupt Controller
      4. 1.3.4 System Control Block (SCB)
    4. 1.4  On-Chip Memory
      1. 1.4.1 SRAM
      2. 1.4.2 Flash
      3. 1.4.3 ROM
    5. 1.5  Power Supply System
      1. 1.5.1 VDDS
      2. 1.5.2 VDDR
      3. 1.5.3 VDDD Digital Core Supply
      4. 1.5.4 DC/DC Converter
    6. 1.6  Radio
    7. 1.7  AES 128-bit Cryptographic Accelerator
    8. 1.8  System Timer (SYSTIM)
    9. 1.9  General Purpose Timers (LGPT)
    10. 1.10 Always-ON (AON) or Ultra-Low Leakage (ULL) Domain
      1. 1.10.1 Watchdog Timer
      2. 1.10.2 Battery and Temperature Monitor
      3. 1.10.3 Real-time Clock (RTC)
      4. 1.10.4 Low Power Comparator
    11. 1.11 Direct Memory Access
    12. 1.12 System Control and Clock
    13. 1.13 Communication Peripherals
      1. 1.13.1 UART
      2. 1.13.2 I2C
      3. 1.13.3 SPI
    14. 1.14 Programmable I/Os
    15. 1.15 Serial Wire Debug (SWD)
  4. 2  Arm Cortex-M0+ Processor
    1. 2.1 Introduction
    2. 2.2 Block Diagram
    3. 2.3 Overview
      1. 2.3.1 Peripherals
      2. 2.3.2 Programmer's Model
      3. 2.3.3 Instruction Set Summary
      4. 2.3.4 Memory Model
    4. 2.4 Registers
      1. 2.4.1 BPU Registers
      2. 2.4.2 CPU_ROM_TABLE Registers
      3. 2.4.3 DCB Registers
      4. 2.4.4 SCB Registers
      5. 2.4.5 SCSCS Registers
      6. 2.4.6 NVIC Registers
      7. 2.4.7 SYSTICK Registers
  5. 3 Memory Map
    1. 3.1 Memory Map
  6. 4 Interrupts and Events
    1. 4.1 Exception Model
      1. 4.1.1 Exception States
      2. 4.1.2 Exception Types
      3. 4.1.3 Exception Handlers
      4. 4.1.4 Vector Table
      5. 4.1.5 Exception Priorities
      6. 4.1.6 Exception Entry and Return
        1. 4.1.6.1 Exception Entry
        2. 4.1.6.2 Exception Return
    2. 4.2 Fault Handling
      1. 4.2.1 Lockup
    3. 4.3 Event Fabric
      1. 4.3.1 Introduction
      2. 4.3.2 Overview
      3. 4.3.3 Registers
      4. 4.3.4 AON Event Fabric
        1. 4.3.4.1 AON Common Input Events List
        2. 4.3.4.2 AON Event Subscribers
        3. 4.3.4.3 Power Management Controller (PMCTL)
        4. 4.3.4.4 Real Time Clock (RTC)
        5. 4.3.4.5 AON to MCU Event Fabric
      5. 4.3.5 MCU Event Fabric
        1. 4.3.5.1 Common Input Event List
        2. 4.3.5.2 MCU Event Subscribers
          1. 4.3.5.2.1 System CPU
          2. 4.3.5.2.2 Non-Maskable Interrupt (NMI)
    4. 4.4 Digital Test Bus (DTB)
    5. 4.5 EVTULL Registers
    6. 4.6 EVTSVT Registers
  7. 5 Debug Subsystem
    1. 5.1  Introduction
    2. 5.2  Block Diagram
    3. 5.3  Overview
      1. 5.3.1 Physical Interface
      2. 5.3.2 Debug Access Ports
    4. 5.4  Debug Features
      1. 5.4.1 Processor Debug
      2. 5.4.2 Breakpoint Unit (BPU)
      3. 5.4.3 Peripheral Debug
    5. 5.5  Behavior in Low Power Modes
    6. 5.6  Restricting Debug Access
    7. 5.7  Mailbox (DSSM)
    8. 5.8  Mailbox Events
      1. 5.8.1 CPU Interrupt Event (AON_DBG_COMB)
    9. 5.9  Software Considerations
    10. 5.10 DBGSS Registers
  8. 6 Power, Reset, and Clocking
    1. 6.1  Introduction
    2. 6.2  System CPU Modes
    3. 6.3  Supply System
      1. 6.3.1 Internal DC/DC Converter and Global LDO
    4. 6.4  Power States
      1. 6.4.1 Reset
      2. 6.4.2 Shutdown
      3. 6.4.3 Active
      4. 6.4.4 Idle
      5. 6.4.5 Standby
    5. 6.5  Digital Power Partitioning
    6. 6.6  Clocks
      1. 6.6.1 CLKSVT
      2. 6.6.2 CLKULL
    7. 6.7  Resets
      1. 6.7.1 Watchdog Timer (WDT)
      2. 6.7.2 LF Loss Detection
    8. 6.8  AON (REG3V3) Register Bank
    9. 6.9  CKMD Registers
    10. 6.10 CLKCTL Registers
    11. 6.11 PMCTL Registers
  9. 7 Internal Memory
    1. 7.1 SRAM
    2. 7.2 VIMS
      1. 7.2.1 Introduction
      2. 7.2.2 Block Diagram
      3. 7.2.3 Cache
        1. 7.2.3.1 Basic Cache Mechanism
        2. 7.2.3.2 Cache Prefetch Mechanism
        3. 7.2.3.3 Cache Micro-Prediction Mechanism
      4. 7.2.4 Flash
        1. 7.2.4.1 Flash Read-Only Protection
        2. 7.2.4.2 Flash Memory Programming
      5. 7.2.5 ROM
    3. 7.3 VIMS Registers
    4. 7.4 FLASH Registers
  10. 8 Device Boot and Bootloader
    1. 8.1 Device Boot and Programming
      1. 8.1.1 Boot Flow
      2. 8.1.2 Boot Timing
      3. 8.1.3 Boot Status
      4. 8.1.4 Boot Protection/Locking Mechanisms
      5. 8.1.5 Debug and Active SWD Connections at Boot
      6. 8.1.6 Flashless Test Mode and Tools Client Mode
        1. 8.1.6.1 Flashless Test Mode
        2. 8.1.6.2 Tools Client Mode
      7. 8.1.7 Retest Mode and Return-to-Factory Procedure
      8. 8.1.8 Disabling SWD Debug Port
    2. 8.2 Flash Programming
      1. 8.2.1 CCFG
      2. 8.2.2 CCFG Permissions/Restrictions that Affect Flash Programming
      3. 8.2.3 SACI Flash Programming Commands
      4. 8.2.4 Flash Programming Flows
        1. 8.2.4.1 Initial Programming of a New Device
        2. 8.2.4.2 Reprogramming of Previously Programmed Device
        3. 8.2.4.3 Add User Record on Already Programmed Device as Part of Commissioning Step
        4. 8.2.4.4 Incrementally Program Ancillary Data to MAIN Flash Sectors of a Previously Programmed Device
        5. 8.2.4.5 Debug Flow Charts
    3. 8.3 Device Management Command Interface
      1. 8.3.1 SACI Communication Protocol
        1. 8.3.1.1 Host Side Protocol
        2. 8.3.1.2 Command Format
        3. 8.3.1.3 Response Format
        4. 8.3.1.4 Response Result Field
        5. 8.3.1.5 Command Sequence Tag
        6. 8.3.1.6 Host Side Timeout
      2. 8.3.2 SACI Commands
        1. 8.3.2.1 Miscellaneous Commands
          1. 8.3.2.1.1 SACI_CMD_MISC_NO_OPERATION
          2. 8.3.2.1.2 SACI_CMD_MISC_GET_DIE_ID
          3. 8.3.2.1.3 SACI_CMD_MISC_GET_CCFG_USER_REC
        2. 8.3.2.2 Debug Commands
          1. 8.3.2.2.1 SACI_CMD_DEBUG_REQ_PWD_ID
          2. 8.3.2.2.2 SACI_CMD_DEBUG_SUBMIT_AUTH
          3. 8.3.2.2.3 SACI_CMD_DEBUG_EXIT_SACI_HALT
          4. 8.3.2.2.4 SACI_CMD_DEBUG_EXIT_SACI_SHUTDOWN
          5. 8.3.2.2.5 SACI_CMD_BLDR_APP_RESET_DEVICE
          6. 8.3.2.2.6 SACI_CMD_BLDR_APP_EXIT_SACI_RUN
        3. 8.3.2.3 Flash Programming Commands
          1. 8.3.2.3.1 SACI_CMD_FLASH_ERASE_CHIP
          2. 8.3.2.3.2 SACI_CMD_FLASH_PROG_CCFG_SECTOR
          3. 8.3.2.3.3 SACI_CMD_FLASH_PROG_CCFG_USER_REC
          4. 8.3.2.3.4 SACI_CMD_FLASH_PROG_MAIN_SECTOR
          5. 8.3.2.3.5 SACI_CMD_FLASH_PROG_MAIN_PIPELINED
          6. 8.3.2.3.6 SACI_CMD_FLASH_VERIFY_MAIN_SECTORS
          7. 8.3.2.3.7 SACI_CMD_FLASH_VERIFY_CCFG_SECTOR
    4. 8.4 Bootloader Support
      1. 8.4.1 Bootloader Parameters
      2. 8.4.2 Persistent State
      3. 8.4.3 User-Defined Bootloader Guidelines
    5. 8.5 ROM Serial Bootloader
      1. 8.5.1 ROM Serial Bootloader Interfaces
        1. 8.5.1.1 Packet Handling
          1. 8.5.1.1.1 Packet Acknowledge and Not-Acknowledge Bytes
        2. 8.5.1.2 Transport Layer
          1. 8.5.1.2.1 UART Transport
            1. 8.5.1.2.1.1 UART Baud Rate Automatic Detection
          2. 8.5.1.2.2 SPI Transport
      2. 8.5.2 ROM Serial Bootloader Parameters
      3. 8.5.3 ROM Serial Bootloader Commands
        1. 8.5.3.1 BLDR_CMD_PING
        2. 8.5.3.2 BLDR_CMD_GET_STATUS
        3. 8.5.3.3 BLDR_CMD_GET_PART_ID
        4. 8.5.3.4 BLDR_CMD_RESET
        5. 8.5.3.5 BLDR_CMD_CHIP_ERASE
        6. 8.5.3.6 BLDR_CMD_CRC32
        7. 8.5.3.7 BLDR_CMD_DOWNLOAD
        8. 8.5.3.8 BLDR_CMD_DOWNLOAD_CRC
        9. 8.5.3.9 BLDR_CMD_SEND_DATA
      4. 8.5.4 Bootloader Firmware Update Example
  11. 9 Device Configuration
    1. 9.1 Factory Configuration (FCFG)
    2. 9.2 Customer Configuration (CCFG)
  12. 10General Purpose Timers (LGPT)
    1. 10.1 Overview
    2. 10.2 Block Diagram
    3. 10.3 Functional Description
      1. 10.3.1  Prescaler
      2. 10.3.2  Counter
      3. 10.3.3  Target
      4. 10.3.4  Channel Input Logic
      5. 10.3.5  Channel Output Logic
      6. 10.3.6  Channel Actions
        1. 10.3.6.1 Period and Pulse Width Measurement
        2. 10.3.6.2 Clear on Zero, Toggle on Compare Repeatedly
        3. 10.3.6.3 Set on Zero, Toggle on Compare Repeatedly
      7. 10.3.7  Channel Capture Configuration
      8. 10.3.8  Channel Filters
        1. 10.3.8.1 Setting up the Channel Filters
      9. 10.3.9  Synchronize Multiple LGPT Timers
      10. 10.3.10 Interrupts, ADC Trigger, and DMA Request
    4. 10.4 Timer Modes
      1. 10.4.1 Quadrature Decoder
      2. 10.4.2 DMA
      3. 10.4.3 IR Generation
      4. 10.4.4 Fault and Park
      5. 10.4.5 Deadband
      6. 10.4.6 Deadband, Fault, and Park
      7. 10.4.7 Example Application: Brushless DC (BLDC) Motor
    5. 10.5 LGPT0 Registers
    6. 10.6 LGPT1 Registers
    7. 10.7 LGPT2 Registers
    8. 10.8 LGPT3 Registers
  13. 11System Timer (SYSTIM)
    1. 11.1 Overview
    2. 11.2 Block Diagram
    3. 11.3 Functional Description
      1. 11.3.1 Common Channel Features
        1. 11.3.1.1 Compare Mode
        2. 11.3.1.2 Capture Mode
        3. 11.3.1.3 Additional Channel Arming Methods
      2. 11.3.2 Interrupts and Events
    4. 11.4 SYSTIM Registers
  14. 12Real Time Clock (RTC)
    1. 12.1 Introduction
    2. 12.2 Block Diagram
    3. 12.3 Interrupts and Events
      1. 12.3.1 Input Event
      2. 12.3.2 Output Event
      3. 12.3.3 Arming and Disarming Channels
    4. 12.4 Capture and Compare Configuration
      1. 12.4.1 Capture
      2. 12.4.2 Compare
    5. 12.5 RTC Registers
  15. 13Low Power Comparator and SYS0
    1. 13.1 Introduction
    2. 13.2 Block Diagram
    3. 13.3 Functional Description
      1. 13.3.1 Input Selection
      2. 13.3.2 Voltage Divider
      3. 13.3.3 Hysteresis
      4. 13.3.4 Wake-Up
    4. 13.4 SYS0 Registers
  16. 14Battery Monitor, Temperature Sensor, and DCDC Controller (PMUD)
    1. 14.1 Introduction
    2. 14.2 Functional Description
      1. 14.2.1 BATMON
      2. 14.2.2 DCDC
    3. 14.3 PMUD Registers
  17. 15Micro Direct Memory Access (µDMA)
    1. 15.1 Introduction
    2. 15.2 Block Diagram
    3. 15.3 Functional Description
      1. 15.3.1  Channel Assignments
      2. 15.3.2  Priority
      3. 15.3.3  Arbitration Size
      4. 15.3.4  Request Types
        1. 15.3.4.1 Single Request
        2. 15.3.4.2 Burst Request
      5. 15.3.5  Channel Configuration
      6. 15.3.6  Transfer Modes
        1. 15.3.6.1 Stop Mode
        2. 15.3.6.2 Basic Mode
        3. 15.3.6.3 Auto Mode
        4. 15.3.6.4 Ping-Pong Mode
        5. 15.3.6.5 Memory Scatter-Gather Mode
        6. 15.3.6.6 Peripheral Scatter-Gather Mode
      7. 15.3.7  Transfer Size and Increments
      8. 15.3.8  Peripheral Interface
      9. 15.3.9  Software Request
      10. 15.3.10 Interrupts and Errors
      11. 15.3.11 Initialization and Configuration
        1. 15.3.11.1 Module Initialization
        2. 15.3.11.2 Configuring a Memory-to-Memory Transfer
        3. 15.3.11.3 Configure the Channel Attributes
        4. 15.3.11.4 Configure the Channel Control Structure
        5. 15.3.11.5 Start the Transfer
        6. 15.3.11.6 Software Considerations
    4. 15.4 DMA Registers
  18. 16Advanced Encryption Standard (AES)
    1. 16.1 Introduction
      1. 16.1.1 AES Performance
    2. 16.2 Functional Description
      1. 16.2.1 Reset Considerations
      2. 16.2.2 Interrupt and Event Support
        1. 16.2.2.1 Interrupt Events and Requests
        2. 16.2.2.2 Connection to Event Fabric
      3. 16.2.3 µDMA
        1. 16.2.3.1 µDMA Example
    3. 16.3 Encryption and Decryption Configuration
      1. 16.3.1  CBC-MAC (Cipher Block Chaining-Message Authentication Code)
      2. 16.3.2  CBC (Cipher Block Chaining) Encryption
      3. 16.3.3  CBC Decryption
      4. 16.3.4  CTR (Counter) Encryption/Decryption
      5. 16.3.5  ECB (Electronic Code Book) Encryption
      6. 16.3.6  ECB Decryption
      7. 16.3.7  CFB (Cipher Feedback) Encryption
      8. 16.3.8  CFB Decryption
      9. 16.3.9  OFB (Open Feedback) Encryption
      10. 16.3.10 OFB Decryption
      11. 16.3.11 PCBC (Propagating Cipher Block Chaining) Encryption
      12. 16.3.12 PCBC Decryption
      13. 16.3.13 CTR-DRBG (Counter-Deterministic Random Bit Generator)
      14. 16.3.14 CCM
    4. 16.4 AES Registers
  19. 17Analog to Digital Converter (ADC)
    1. 17.1 Overview
    2. 17.2 Block Diagram
    3. 17.3 Functional Description
      1. 17.3.1  ADC Core
      2. 17.3.2  Voltage Reference Options
      3. 17.3.3  Resolution Modes
      4. 17.3.4  ADC Clocking
      5. 17.3.5  Power-Down Behavior
      6. 17.3.6  Sampling Trigger Sources and Sampling Modes
        1. 17.3.6.1 AUTO Sampling Mode
        2. 17.3.6.2 MANUAL Sampling Mode
      7. 17.3.7  Sampling Period
      8. 17.3.8  Conversion Modes
      9. 17.3.9  ADC Data Format
      10. 17.3.10 Status Register
      11. 17.3.11 ADC Events
        1. 17.3.11.1 CPU Interrupt Event Publisher (INT_EVENT0)
        2. 17.3.11.2 Generic Event Publisher (INT_EVENT1)
        3. 17.3.11.3 DMA Trigger Event Publisher (INT_EVENT2)
        4. 17.3.11.4 Generic Event Subscriber
    4. 17.4 Advanced Features
      1. 17.4.1 Window Comparator
      2. 17.4.2 DMA and FIFO Operation
        1. 17.4.2.1 DMA/CPU Operation in Non-FIFO Mode (FIFOEN=0)
        2. 17.4.2.2 DMA/CPU Operation in FIFO Mode (FIFOEN=1)
        3. 17.4.2.3 DMA/CPU Operation Summary Matrix
      3. 17.4.3 Ad-Hoc Single Conversion
    5. 17.5 ADC Registers
  20. 18I/O Controller (IOC)
    1. 18.1  Introduction
    2. 18.2  Block Diagram
    3. 18.3  I/O Mapping and Configuration
      1. 18.3.1 Basic I/O Mapping
      2. 18.3.2 Radio GPO
      3. 18.3.3 Pin Mapping
      4. 18.3.4 DTB Muxing
    4. 18.4  Edge Detection
    5. 18.5  GPIO
    6. 18.6  I/O Pins
    7. 18.7  Unused Pins
    8. 18.8  Debug Configuration
    9. 18.9  IOC Registers
    10. 18.10 GPIO Registers
  21. 19Universal Asynchronous Receiver/Transmitter (UART)
    1. 19.1 Introduction
    2. 19.2 Block Diagram
    3. 19.3 Functional Description
      1. 19.3.1 Transmit and Receive Logic
      2. 19.3.2 Baud Rate Generation
      3. 19.3.3 FIFO Operation
        1. 19.3.3.1 FIFO Remapping
      4. 19.3.4 Data Transmission
      5. 19.3.5 Flow Control
      6. 19.3.6 IrDA Encoding and Decoding
      7. 19.3.7 Interrupts
      8. 19.3.8 Loopback Operation
    4. 19.4 Interface to µDMA
    5. 19.5 Initialization and Configuration
    6. 19.6 UART Registers
  22. 20Serial Peripheral Interface (SPI)
    1. 20.1 Overview
      1. 20.1.1 Features
      2. 20.1.2 Block Diagram
    2. 20.2 Signal Description
    3. 20.3 Functional Description
      1. 20.3.1  Clock Control
      2. 20.3.2  FIFO Operation
        1. 20.3.2.1 Transmit FIFO
        2. 20.3.2.2 Repeated Transmit Operation
        3. 20.3.2.3 Receive FIFO
        4. 20.3.2.4 FIFO Flush
      3. 20.3.3  Interrupts
      4. 20.3.4  Data Format
      5. 20.3.5  Delayed Data Sampling
      6. 20.3.6  Chip Select Control
      7. 20.3.7  Command Data Control
      8. 20.3.8  Protocol Descriptions
        1. 20.3.8.1 Motorola SPI Frame Format
        2. 20.3.8.2 Texas Instruments Synchronous Serial Frame Format
        3. 20.3.8.3 MICROWIRE Frame Format
      9. 20.3.9  CRC Configuration
      10. 20.3.10 Auto CRC Functionality
      11. 20.3.11 Auto Header Functionality
      12. 20.3.12 SPI Status
      13. 20.3.13 Debug Halt
    4. 20.4 µDMA Operation
    5. 20.5 Initialization and Configuration
    6. 20.6 SPI Registers
  23. 21Inter-Integrated Circuit (I2C)
    1. 21.1 Introduction
    2. 21.2 Block Diagram
    3. 21.3 Functional Description
      1. 21.3.1 Functional Overview
        1. 21.3.1.1 Start and Stop Conditions
        2. 21.3.1.2 Data Format with 7-Bit Address
        3. 21.3.1.3 Data Validity
        4. 21.3.1.4 Acknowledge
        5. 21.3.1.5 Arbitration
      2. 21.3.2 Available Speed Modes
      3. 21.3.3 Interrupts
        1. 21.3.3.1 I2C Controller Interrupts
        2. 21.3.3.2 I2C Target Interrupts
      4. 21.3.4 Loopback Operation
      5. 21.3.5 Command Sequence Flow Charts
        1. 21.3.5.1 I2C Controller Command Sequences
        2. 21.3.5.2 I2C Target Command Sequences
    4. 21.4 Initialization and Configuration
    5. 21.5 I2C Registers
  24. 22Radio
    1. 22.1 Introduction
    2. 22.2 Block Diagram
    3. 22.3 Overview
      1. 22.3.1 Radio Sub-Domains
      2. 22.3.2 Radio RAMs
      3. 22.3.3 Doorbell (DBELL)
        1. 22.3.3.1 Interrupts
        2. 22.3.3.2 GPIO Control
        3. 22.3.3.3 SYSTIM Interface
    4. 22.4 Radio Usage Model
      1. 22.4.1 CRC and Whitening
    5. 22.5 LRFDDBELL Registers
    6. 22.6 LRFDRXF Registers
    7. 22.7 LRFDTXF Registers
  25. 23Revision History

5.7 Mailbox (DSSM)

The debug subsystem mailbox (DSSM) enables a debug probe to pass messages to the target device through the SWD interface, and for the target device to return data to the debug probe.

The DSSM supports the following functions:

  • Transmission of commands to the device during boot, including authenticating the debug probe for password-protected debug, mass erase, and factory reset operations
  • Communicating with application software running on the target device when no other communication interface is present

32-bit word data buffers are provided for transmit data (debug probe to target device) and receive data (target device to debug probe). These data buffers are implemented as the 32-bit memory-mapped registers DBGSS.TXD and DBGSS.RXD. The DBGSS.TXCTL and DBGSS.RXCTL registers are provided for enabling flow control and indicating status of the mailbox.

Table 5-4 DBGSS DSSM Register Functions
DBGSS RegisterDescriptionDebug ProbeTarget DeviceActions
TXDData bufferRWRDBGSS.TXCTL[0] TXDSTA bit is set on write by the debug probe, and cleared on a read by the target device. DBGSS.RIS[0] TXIFG bit is also set on a write by the debug probe.
TXCTLFlow control and statusRWRNone
RXDData bufferRRWDBGSS.RXCTL[0] RXDSTA bit is set on write by the target device, and cleared on a read by the debug probe. DBGSS.RIS[1] RXIFG bit is also set on a write by the target device
RXCTLFlow control and statusRRWNone

The DBGSS.TXCTL[0] TRANSMIT bit is set in the TXCTL register when a debug probe writes data to the DBGSS.TXD buffer register. The TRANSMIT flag remains set until the target device reads DBGSS.TXD or a POR occurs. The DBGSS.RXCTL[0] RECEIVE bit is set when the target device writes data to the DBGSS.RXD buffer register. The RECEIVE flag remains set until the debug probe or target device reads the data from DBGSS.RXD.

Software running on the target device cannot write to TXD, and software cannot clear the TRANSMIT flag other than by reading DGBSS.TXD. The DBGSS.TXCTL[7:1] bit field contains flag bits which can be set or cleared by the debug probe to implement a protocol if desired. Only the debug probe can write to the TRANSMIT_FLAGS field in TXCTL.

In a similar way, only the target device software can write to DBGSS.RXD and DBGSS.RXCTL. The debug probe cannot write to RX_DATA and can only clear the DEBUGSS.RXCTL[0] RECEIVE bit by reading DBGSS.RXD. DBGSS.RXCTL[7:1] FLAGS bit field contains flag bits. Software on the target device can set or clear bits in the DBGSS.RXCTL[7:1] FLAGS field to implement a protocol if desired. These flags can be read by the debug probe but can not be modified by the debug probe.

DBGSS.TXDPEEK and DBGSS.RXDPEEK registers can be read by the device to read DBGSS.TXD and DBGSS.RXD registers without affecting the FULL/EMPTY flag.

For a complete listing of commands that are supported by the boot configuration routine during device startup configuration, see Chapter 8.