Datasheet
Table Of Contents
- RP2040 Datasheet
- Colophon
- Chapter 1. Introduction
- Chapter 2. System Description
- 2.1. Bus Fabric
- 2.2. Address Map
- 2.3. Processor subsystem
- 2.4. Cortex-M0+
- 2.4.1. Features
- 2.4.2. Functional Description
- 2.4.3. Programmer’s model
- 2.4.4. System control
- 2.4.5. NVIC
- 2.4.6. MPU
- 2.4.7. Debug
- 2.4.8. List of Registers
- 2.5. Memory
- 2.6. Boot Sequence
- 2.7. Bootrom
- 2.7.1. Bootrom Source
- 2.7.2. Processor Controlled Boot Sequence
- 2.7.3. Bootrom Contents
- 2.7.4. USB Mass Storage Interface
- 2.7.5. USB PICOBOOT Interface
- 2.8. Power Supplies
- 2.9. On-Chip Voltage Regulator
- 2.10. Power Control
- 2.11. Chip-Level Reset
- 2.12. Power-On State Machine
- 2.13. Subsystem Resets
- 2.14. Clocks
- 2.14.1. Overview
- 2.14.2. Clock sources
- 2.14.2.1. Ring Oscillator
- 2.14.2.1.1. Mitigating ROSC frequency variation due to process
- 2.14.2.1.2. Mitigating ROSC frequency variation due to voltage
- 2.14.2.1.3. Mitigating ROSC frequency variation due to temperature
- 2.14.2.1.4. Automatic mitigation of ROSC frequency variation due to PVT
- 2.14.2.1.5. Automatic overclocking using the ROSC
- 2.14.2.2. Crystal Oscillator
- 2.14.2.3. External Clocks
- 2.14.2.4. Relaxation Oscillators
- 2.14.2.5. PLLs
- 2.14.2.1. Ring Oscillator
- 2.14.3. Clock Generators
- 2.14.4. Frequency Counter
- 2.14.5. Resus
- 2.14.6. Programmer’s Model
- 2.14.7. List of registers
- 2.15. Crystal Oscillator (XOSC)
- 2.16. Ring Oscillator (ROSC)
- 2.17. PLL
- 2.18. GPIO
- 2.19. Sysinfo
- 2.20. Syscfg
- Chapter 3. PIO
- Chapter 4. Peripherals
- 4.1. USB
- 4.2. DMA
- 4.3. UART
- 4.4. I2C
- 4.4.1. Features
- 4.4.2. IP Configuration
- 4.4.3. I2C Overview
- 4.4.4. I2C Terminology
- 4.4.5. I2C Behaviour
- 4.4.6. I2C Protocols
- 4.4.7. Tx FIFO Management and START, STOP and RESTART Generation
- 4.4.8. Multiple Master Arbitration
- 4.4.9. Clock Synchronization
- 4.4.10. Operation Modes
- 4.4.11. Spike Suppression
- 4.4.12. Fast Mode Plus Operation
- 4.4.13. Bus Clear Feature
- 4.4.14. IC_CLK Frequency Configuration
- 4.4.15. DMA Controller Interface
- 4.4.16. List of Registers
- 4.5. SPI
- 4.5.1. Overview
- 4.5.2. Functional Description
- 4.5.3. Operation
- 4.5.3.1. Interface reset
- 4.5.3.2. Configuring the SSP
- 4.5.3.3. Enable PrimeCell SSP operation
- 4.5.3.4. Clock ratios
- 4.5.3.5. Programming the SSPCR0 Control Register
- 4.5.3.6. Programming the SSPCR1 Control Register
- 4.5.3.7. Frame format
- 4.5.3.8. Texas Instruments synchronous serial frame format
- 4.5.3.9. Motorola SPI frame format
- 4.5.3.10. Motorola SPI Format with SPO=0, SPH=0
- 4.5.3.11. Motorola SPI Format with SPO=0, SPH=1
- 4.5.3.12. Motorola SPI Format with SPO=1, SPH=0
- 4.5.3.13. Motorola SPI Format with SPO=1, SPH=1
- 4.5.3.14. National Semiconductor Microwire frame format
- 4.5.3.15. Examples of master and slave configurations
- 4.5.3.16. PrimeCell DMA interface
- 4.5.4. List of Registers
- 4.6. PWM
- 4.7. Timer
- 4.8. Watchdog
- 4.9. RTC
- 4.10. ADC and Temperature Sensor
- 4.11. SSI
- 4.11.1. Overview
- 4.11.2. Features
- 4.11.3. IP Modifications
- 4.11.4. Clock Ratios
- 4.11.5. Transmit and Receive FIFO Buffers
- 4.11.6. 32-Bit Frame Size Support
- 4.11.7. SSI Interrupts
- 4.11.8. Transfer Modes
- 4.11.9. Operation Modes
- 4.11.10. Partner Connection Interfaces
- 4.11.11. DMA Controller Interface
- 4.11.12. APB Interface
- 4.11.13. List of Registers
- Chapter 5. Electrical and Mechanical
- Appendix A: Register Field Types
- Appendix B: Errata
2.5.3.2. Cache Flushing and Maintenance
The FLUSH register allows the entire cache contents to be flushed. This is necessary if software has reprogrammed the
flash contents, and needs to clear out stale data and code, without performing a reboot.
Flushing the cache whilst accessing flash data (perhaps initiating the flush on one core whilst another core may be
executing code from flash data) is a safe operation, but any master accessing flash data while the flush is in progress will
be stalled until completion. The flush is implemented by zeroing the cache tag memory using an internal counter, which
takes around 2000 clock cycles.
A complete cache flush dramatically slows subsequent code execution, until the cache "warms up" again. There is an
alternative, which allows cache contents corresponding to only a certain address range to be invalidated. A write to the
0x10… mirror will look up the addressed location in the cache, and delete any matching entry found. Writing to all word-
aligned locations in an address range (e.g. a flash sector that has just been erased and reprogrammed) therefore
eliminates the possibility of stale cached data in this range, without suffering the effects of a complete cache flush.
Pico Examples: https://github.com/raspberrypi/pico-examples/tree/pre_release/flash/cache_perfctr/flash_cache_perfctr.c Lines 30 - 55
30 // Flush cache to make sure we miss the first time we access test_data
31 xip_ctrl_hw->flush = 1;
32 while (!(xip_ctrl_hw->stat & XIP_STAT_FLUSH_READY_BITS))
33 tight_loop_contents();
34
35 // Clear counters (write any value to clear)
36 xip_ctrl_hw->ctr_acc = 1;
37 xip_ctrl_hw->ctr_hit = 1;
38
39 (void) *test_data_ptr;
40 check(xip_ctrl_hw->ctr_hit == 0 && xip_ctrl_hw->ctr_acc == 1,
41 "First access to data should miss");
42
43 (void) *test_data_ptr;
44 check(xip_ctrl_hw->ctr_hit == 1 && xip_ctrl_hw->ctr_acc == 2,
45 "Second access to data should hit");
46
47 // Write to invalidate individual cache lines (64 bits)
48 // Writes must be directed to the cacheable, allocatable alias (address 0x10.._....)
49 *test_data_ptr = 0;
50 (void) *test_data_ptr;
51 check(xip_ctrl_hw->ctr_hit == 1 && xip_ctrl_hw->ctr_acc == 3,
52 "Should miss after invalidation");
53 (void) *test_data_ptr;
54 check(xip_ctrl_hw->ctr_hit == 2 && xip_ctrl_hw->ctr_acc == 4,
55 "Second access after invalidation should hit again");
2.5.3.3. SSI
The execute-in-place functionality is provided by the SSI interface, documented in SSI. It supports 1, 2 or 4-bit SPI flash
interfaces (SPI, DSPI and QSPI), and can insert either an instruction prefix or mode continuation bits on each XIP access.
This includes the possibility of issuing a standard 03h serial flash read command for each access, allowing virtually any
serial flash device to be used. The maximum SPI clock frequency is half the system clock frequency.
The SSI can also be used as a standard FIFO-based SPI master, with DMA support. This mode is used by the bootrom to
extract the second stage bootloader from external flash (see Section 2.7.2). The bus interposer allows an atomic set, clear
or XOR operation to be posted to SSI control registers, in the same manner as other memory-mapped IO on RP2040. This
is described in more detail in Section 2.1.2.
RP2040 Datasheet
2.5. Memory 108