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

/**
 * FILE: coprocessor.s
 *
 * DESCRIPTION:
 * RP2350 Coprocessor Access Functions.
 * 
 * BRIEF:
 * Provides functions to enable coprocessor access control.
 *
 * 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   Enable coprocessor access.
 *
 * @details Grants full access to coprocessor 0 via CPACR.
 *
 * @param   None
 * @retval  None
 */
.global Enable_Coprocessor
.type Enable_Coprocessor , %function
Enable_Coprocessor:
  ldr   r0, =CPACR                               // load CPACR address
  ldr   r1, [r0]                                 // read CPACR value
  orr   r1, r1, #(1<<1)                          // set CP0: Ctrl access priv coproc 0 bit
  orr   r1, r1, #(1<<0)                          // set CP0: Ctrl access priv coproc 0 bit
  str   r1, [r0]                                 // store value into CPACR
  dsb                                            // data sync barrier
  isb                                            // instruction sync barrier
  bx    lr                                       // return