handlerUARTjedi2.s

#UARTinterr:
    # There is space on _uart_buff
    # _uart_buff[0]=UARTstatus, [1]=UARTcontrol, [2]=data_inp, [3]=new,
    #           [4]=$ra, [5]=$a0, [6]=$a1, [7]=$a2, [8]=$a3
    #k0 = _uart_buff

    andi  $a1, $k1, UART_rx_irq # Is this reception?
    beq   $a1, $zero, UARTret   #   no, maybe transmission?
    nop

    #handle reception
    lw    $a1, 4($a0)           # Read data from device
    nop                         #   and store it to UART's buffer
    sw    $a1, 2*4($k0)         #   and return from interrupt
    addiu $a1, $zero, 1
    sw    $a1, 3*4($k0)         # Signal new arrival
                                # Jedian: when a new char is on the UART's buffer, 
                                #         i have to enqueue it and update nrx.

    # saving used registers on _uart_buff
    sw    $5, 9*4($k0)
    sw    $6, 10*4($k0)
    sw    $7, 11*4($k0)
    
    # check if queue is full, maybe increment
    lui   $5, %hi(nrx)
    ori   $5, $5, %lo(nrx)
    lw    $7, 0($5)
    slti  $6, $7, 16
    beq   $6, zero, overrun
    nop
    addiu $7, $7, 1
    sw    $7, 0($5)

    # enqueue
    lui   $5, %hi(rx_tl)        # get rx tail address
    ori   $5, $5, %lo(rx_tl)    

    lw    $7, 0($5)
    nop
    addiu $7, $7, 1             # increment in 1 the tail of the circular queue
    andi  $7, $7, 0xf           # % 16
    sw    $7, 0($5)

    #### stores on queue on tail
    lui   $6, %hi(rx_q)         # get queue address
    ori   $6, $6, %lo(rx_q)

    addu  $6, $7, $6            # calculate address to move new char
    lw    $7, 2*4($k0)          # get char to be stored
    nop
    sb    $7, 0($6)             # and store it!

    #### process rx_tl -- update tail
    #lw   $7, 0($5)
    #nop

overrun:

    # do something if queue is full
    #... (doing absolutely nothing besides stacking and unstacking regs)

    # loading back used registers
    lw    $5, 9*4($k0)
    lw    $6, 10*4($k0)
    lw    $7, 11*4($k0)

    #Precisa coisar o nrx (incrementar)

#UARTinterr2:
#    andi  $a1, $k1, UART_tx_irq # Is this transmission?
#    beq   $a1, $zero, UARTret   # no, ignore it and return
#    nop

    #handle transmission
    # ... TODO

    # Lembrar de inicializar os hd e tl com 0 no comeco do main

#UARTret: