Datasheet

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001: X (scratch register X)
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010: Y (scratch register Y)
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011: NULL (all zeroes)
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100: Reserved
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101: Reserved
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110: ISR
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111: OSR
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Bit count: How many bits to shift into the ISR. 1…32 bits, 32 is encoded as 00000.
If automatic push is enabled, IN will also push the ISR contents to the RX FIFO if the push threshold is reached
(SHIFTCTRL_PUSH_THRESH). IN still executes in one cycle, whether an automatic push takes place or not. The state machine
will stall if the RX FIFO is full when an automatic push occurs. An automatic push clears the ISR contents to all-zeroes,
and clears the input shift count. See Section 3.5.4.
IN always uses the least significant Bit count bits of the source data. For example, if PINCTRL_IN_BASE is set to 5, the
instruction IN PINS, 3 will take the values of pins 5, 6 and 7, and shift these into the ISR. First the ISR is shifted to the left
or right to make room for the new input data, then the input data is copied into the gap this leaves. The bit order of the
input data is not dependent on the shift direction.
NULL can be used for shifting the ISR’s contents. For example, UARTs receive the LSB first, so must shift to the right.
After 8 IN PINS, 1 instructions, the input serial data will occupy bits 31…24 of the ISR. An IN NULL, 24 instruction will shift
in 24 zero bits, aligning the input data at ISR bits 7…0. Alternatively, the processor or DMA could perform a byte read
from FIFO address + 3, which would take bits 31…24 of the FIFO contents.
3.4.4.3. Assembler Syntax
in <source>, <bit_count>
where:
<source> Is one of the sources specified above.
<bit_count> Is a value (see Section 3.3.2) specifying the number of bits to shift (valid range 1-32)
3.4.5. OUT
3.4.5.1. Encoding
Bit: 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
OUT
0 1 1 Delay/side-set Destination Bit count
3.4.5.2. Operation
Shift Bit count bits out of the Output Shift Register (OSR), and write those bits to Destination. Additionally, increase the
output shift count by Bit count, saturating at 32.
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Destination:
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000: PINS
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001: X (scratch register X)
RP2040 Datasheet
3.4. Instruction Set 344