AREA myCODE, CODE, READONLY          ; Start of the code section 

    EXPORT Start                         ; Export the Start function
    EXTERN setPortF                      ; External function to initialize Port F
    EXTERN setPortFInterrupts            ; External function to configure Port F interrupts
    EXPORT GPIOPortF_Handler             ; Export the interrupt handler
    EXTERN delay                         ; External delay function
     
GPIO_PORTF_DATA_R  EQU 0x400253FC        ; Address of GPIO Port F data register
GPIOF_ICR          EQU 0x4002541C        ; GPIO Port F Interrupt Clear register
GPIOF_MIS          EQU 0x40025418        ; GPIO Port F Masked Interrupt Status register
 
SW1                EQU 0x10              ; PF4 (Switch 1) bit mask
SW2                EQU 0x01              ; PF0 (Switch 2) bit mask
 
Start PROC
    BL setPortF                          ; Initialize Port F
    BL setPortFInterrupts                ; Configure Port F interrupts
    BX LR                                ; Exit the Start function
    ENDP
 
GPIOPortF_Handler PROC
    LDR R0, =GPIOF_MIS                  ; Load the address of the Masked Interrupt Status register
    LDR R1, [R0]                        ; Read the value from the GPIO Port F Interrupt Masked Status register
 
    ; Check if the interrupt is triggered by SW1 (PF4)
    TST R1, #SW1                        ; Perform bitwise AND to check if SW1 was pressed (bit 4 is set)
    BEQ Check_SW2                       ; If no interrupt from SW1, check SW2
 
    LDR R0, =GPIO_PORTF_DATA_R          ; Load the address of the GPIO Port F data register
    MOV R4, #0x02                       ; Set the value to 0x02 (turn on red LED)
    ADD R5, R5, R4                      ; Add to R5 (increment logic)
    STR R5, [R0]                        ; Write the value to the GPIO Port F data register
    CMP R5, #0x0A                       ; Compare R5 with 0x0A
    BEQ reverse                         ; Jump to reverse if equal

    ; Clear the interrupt flag for SW1
    LDR R0, =GPIOF_ICR                  ; Load the address of the Interrupt Clear register
    MOV R2, #SW1                        ; Set the value for PF4 (SW1) to clear the interrupt
    STR R2, [R0]                        ; Write to GPIOF_ICR to clear the interrupt flag
    BX LR                               ; Exit the interrupt handler
 
Check_SW2
    ; Check if the interrupt is triggered by SW2 (PF0)
    TST R1, #SW2                        ; Perform bitwise AND to check if SW2 was pressed (bit 0 is set)
    BEQ Done_Handler                    ; If no interrupt from SW2, exit the handler
 
    LDR R0, =GPIO_PORTF_DATA_R          ; Load the address of the GPIO Port F data register
    MOV R7, #0x02                       ; Set the value to 0x02 (turn off or change LED)
    SUB R5, R5, R7                      ; Subtract from R5 (decrement logic)
    STR R5, [R0]                        ; Write the value to the GPIO Port F data register
    CMP R5, #0x00                       ; Compare R5 with 0x00
    BEQ reverse2                        ; Jump to reverse2 if equal

    ; Clear the interrupt flag for SW2
    LDR R0, =GPIOF_ICR                  ; Load the address of the Interrupt Clear register
    MOV R2, #SW2                        ; Set the value for PF0 (SW2) to clear the interrupt
    STR R2, [R0]                        ; Write to GPIOF_ICR to clear the interrupt flag

Done_Handler
    BX LR                               ; Exit the interrupt handler
    ENDP

reverse
    MOV R5, #0x00                       ; Reset R5
    BX LR                               ; Exit the handler

reverse2
    MOV R5, #0x08                       ; Set R5 to specific value
    BX LR                               ; Exit the handler

    ALIGN
    END