Embedded-Hacking/drivers/0x01_uart_asm_arm/reset.s

/**
 * FILE: reset.s
 *
 * DESCRIPTION:
 * RP2350 Reset Controller Functions.
 *
 * BRIEF:
 * Provides functions to initialize subsystems by clearing their
 * reset bits in the Reset controller.
 *
 * AUTHOR: Kevin Thomas
 * CREATION DATE: November 27, 2025
 * UPDATE DATE: November 27, 2025
 */

.syntax unified                                  // use unified assembly syntax
.cpu cortex-m33                                  // target Cortex-M33 core
.thumb                                           // use Thumb instruction set

.include "constants.s"

/**
 * Initialize the .text section. 
 * The .text section contains executable code.
 */
.section .text                                   // code section
.align 2                                         // align to 4-byte boundary

/**
 * @brief   Init subsystem.
 *
 * @details Initiates the various subsystems by clearing their reset bits.
 *
 * @param   None
 * @retval  None
 */
.global Init_Subsystem
.type Init_Subsystem, %function
Init_Subsystem:
.GPIO_Subsystem_Reset:
  ldr   r0, =RESETS_RESET                        // load RESETS->RESET address
  ldr   r1, [r0]                                 // read RESETS->RESET value
  bic   r1, r1, #(1<<6)                          // clear IO_BANK0 bit
  str   r1, [r0]                                 // store value into RESETS->RESET address
.GPIO_Subsystem_Reset_Wait:
  ldr   r0, =RESETS_RESET_DONE                   // load RESETS->RESET_DONE address
  ldr   r1, [r0]                                 // read RESETS->RESET_DONE value
  tst   r1, #(1<<6)                              // test IO_BANK0 reset done
  beq   .GPIO_Subsystem_Reset_Wait               // wait until done
  bx    lr                                       // return