/**
 * FILE: main.s
 *
 * DESCRIPTION:
 * RP2350 Bare-Metal UART Main Application.
 * 
 * BRIEF:
 * Main application entry point for RP2350 UART driver. Contains the
 * main loop that echoes UART input to output.
 *
 * AUTHOR: Kevin Thomas
 * CREATION DATE: November 2, 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   Main application entry point.
 *
 * @details Implements the infinite echo loop.
 *
 * @param   None
 * @retval  None
 */
.global main                                     // export main
.type main, %function                            // mark as function
main:
.Push_Registers:
  push  {r4-r12, lr}                             // push registers r4-r12, lr to the stack
.Loop:
  bl    UART0_In                                 // call UART0_In
  bl    UART0_Out                                // call UART0_Out
  b     .Loop                                    // loop forever
.Pop_Registers:
  pop   {r4-r12, lr}                             // pop registers r4-r12, lr from the stack
  bx    lr                                       // return to caller

/**
 * Test data and constants.
 * The .rodata section is used for constants and static data.
 */
.section .rodata                                 // read-only data section

/**
 * Initialized global data.
 * The .data section is used for initialized global or static variables.
 */
.section .data                                   // data section

/**
 * Uninitialized global data.
 * The .bss section is used for uninitialized global or static variables.
 */
.section .bss                                    // BSS section