Datasheet

2.13.2. Programmer’s Model
The Pico SDK defines a struct to represent the resets registers.
Pico SDK: https://github.com/raspberrypi/pico-sdk/tree/pre_release/src/rp2040/hardware_structs/include/hardware/structs/resets.h Lines 13 - 19
13 typedef struct {
14 io_rw_32 reset;
15 io_rw_32 wdsel;
16 io_rw_32 reset_done;
17 } resets_hw_t;
18
19 #define resets_hw ((resets_hw_t *const)RESETS_BASE)
Three registers are defined:
•
reset: this register contains a bit for each peripheral that can be reset. If the bit is set to 1 then the reset is asserted. If
the bit is cleared then the reset is deasserted.
•
wdsel: if the bit is set then this peripheral will be reset if the watchdog fires (note that the power on state machine
can potentially reset the whole reset controller, which will reset everything)
•
reset_done: a bit for each peripheral, that gets set once the peripheral is out of reset. This allows software to wait for
this status bit in case the peripheral has some initialisation to do before it can be used.
The reset functions in the Pico SDK are defined as follows:
Pico SDK: https://github.com/raspberrypi/pico-sdk/tree/pre_release/src/rp2_common/hardware_resets/include/hardware/resets.h Lines 75 - 77
75 static inline void unreset_block(uint32_t bits) {
76 hw_clear_bits(&resets_hw->reset, bits);
77 }
Pico SDK: https://github.com/raspberrypi/pico-sdk/tree/pre_release/src/rp2_common/hardware_resets/include/hardware/resets.h Lines 75 - 77
75 static inline void unreset_block(uint32_t bits) {
76 hw_clear_bits(&resets_hw->reset, bits);
77 }
Pico SDK: https://github.com/raspberrypi/pico-sdk/tree/pre_release/src/rp2_common/hardware_resets/include/hardware/resets.h Lines 84 - 88
84 static inline void unreset_block_wait(uint32_t bits) {
85 hw_clear_bits(&resets_hw->reset, bits);
86 while (~resets_hw->reset_done & bits)
87 tight_loop_contents();
88 }
An example use of these is in the UART driver, where the driver defines a uart_reset function, selecting a different bit of
the reset register depending on the uart specified:
Pico SDK: https://github.com/raspberrypi/pico-sdk/tree/pre_release/src/rp2_common/hardware_uart/uart.c Lines 30 - 38
30 static inline void uart_reset(uart_inst_t *uart) {
31 invalid_params_if(UART, uart != uart0 && uart != uart1);
32 reset_block(uart_hw_index(uart) ? RESETS_RESET_UART1_BITS : RESETS_RESET_UART0_BITS);
33 }
34
RP2040 Datasheet
2.13. Subsystem Resets 157