Datasheet

Table 156.
STREAM_CTR Register
Bits Name Description Type Reset
31:22 Reserved. - - -
21:0 NONAME Write a nonzero value to start a streaming read. This will
then
progress in the background, using flash idle cycles to
transfer
a linear data block from flash to the streaming FIFO.
Decrements automatically (1 at a time) as the stream
progresses, and halts on reaching 0.
Write 0 to halt an in-progress stream, and discard any in-
flight
read, so that a new stream can immediately be started
(after
draining the FIFO and reinitialising STREAM_ADDR)
RW 0x000000
STREAM_FIFO Register
Description
FIFO stream data
Table 157.
STREAM_FIFO
Register
Bits Name Description Type Reset
31:0 NONAME Streamed data is buffered here, for retrieval by the system
DMA.
This FIFO can also be accessed via the XIP_AUX slave, to
avoid exposing
the DMA to bus stalls caused by other XIP traffic.
RF 0x00000000
2.6. Boot Sequence
Several components of the RP2040 work together to get to a point where the processors are out of reset and able to run
the Bootrom. The bootrom is software that is built into the chip, performing the "processor controlled" part of the boot
sequence. We will refer to the steps before the processor is running as the "hardware controlled" boot sequence.
The hardware controlled boot sequence is as follows:
•
Power is applied to the chip and the RUN pin is high. (If RUN is low then the chip will be held in reset.)
•
The On-Chip Voltage Regulator waits until the digital core supply (DVDD) is stable
•
The Power-On State Machine is started. To summarise the sequence:
◦
The Ring Oscillator is started, providing a clock source to the clock generators. clk_sys and clk_ref are now
running at a relatively low frequency (typically 6.5MHz).
◦
The reset controller (Subsystem Resets), the execute-in-place hardware (Execute-In-Place), memories (see
SRAM and ROM), Bus Fabric, and Processor Subsystem is taken out of reset.
◦
Processor core 0 and core 1 begin to execute the Bootrom.
2.7. Bootrom
The Bootrom size is limited to 16 kB. It contains: The Bootrom size is limited to 16 kB. It contains:
•
Processor core 0 initial boot sequence.
RP2040 Datasheet
2.6. Boot Sequence 113