PLP:计时器和按钮中断服务例程

Question

所以我很难弄清楚如何触发计时器中断(每200个周期(和按钮中断。当我按下按钮中断时，似乎要做的就是暂时暂停柜台拆分一秒钟，然后继续计数。然后，无论我多久单击PLP，它都不会注册另一个按钮中断。按钮中断要做的是设置寄存器$ A1至1(或非零号(，该寄存器应重置计数器。计时器中断应该在每200个周期上闪烁LED，然后在另一个200个周期之后熄灭。已经提供了七个段显示代码，因此它的作用仅为0-9，然后是A-F，然后从10s开始。因此11，12，...，19，1a，1b，...，1f，20等。

.org 0x10000000
li $sp, 0x10fffffc  # Stack pointer initialization
li $s0, sseg_lut    # Lookup table address used by sseg_display
lui $s1, 0xf070 # Interrupt controller register
lui $s2, 0xf0a0 # Seven segment display

# TODO: enable interrupts here:
# ************************************************************
# Interrupt Initialization
li $t2, 0b1011 #value used to enable the used interrupts
li $t4, 0b00000000 #value used to check if LEDs are off
li $t5, 0b11111111 #value used to check if LEDs are on
li $t6, 0xf0600000 #address of the Timer
li $t7, 0xC8 #number of cycles we want the timer interrupt to be triggered 
sw $t7, 0($t6) #Store value onto timer in order to trigger interrupt????????????????
li $t8, 0xf0200000 #address of LEDs
sw $t2, 0($s1) #set mask register to enable the used interrupts including Global Interrupt Enable 
li $iv, isr #interrupt vector 
# ************************************************************
main:
    jal sseg_display
    nop
    addiu $a0, $a0, 1
    beq $a1, $0, no_counter_reset
        nop
        move $a0, $0
        move $a1, $0
    no_counter_reset:
    j main
    nop

# TODO: add interrupt service routine here:
# ************************************************************
# Interrupt Service Routine
isr: 
    save
    li $t0, 0b0011 #value used to check for timer interrupt
    li $t1, 0b1001 #value used to check for button interrupt
    lw $i0, 0($t8) #check what is stored currently on LEDs
    lw $i1, 4($s1) #load what value is in the status register
    j mainISR
    nop
    mainISR:
        beq $i1, $t0, timerInterrupt #check if the interrupt was triggered by timer
        nop
        beq $i1, $t1, buttonInterrupt #check if interrupt was triggered by button
        nop
        timerInterrupt: 
            beq $t4, $i0, turnOnLEDs #If the LEDs are off, go to the loop to turn them on
            nop
            bne $t4, $i0, turnOffLEDs #If the LEDs are on, go to the loop to turn them off 
            nop
            turnOnLEDs:
                sw $t5, 0($t8) #Stores the value to the LEDs to turn them all on 
                li $i1, 0b1001 #Bits used to clear interrupt in status register 
                j endISR #Jump to the end of the isr 
                nop
            turnOffLEDs:
                sw $t4, 0($t8) #Stores the value to the LEDs to turn them all off 
                li $i1, 0b1001 #Bits used to clear interrup in status register 
                j endISR #Jump to the end of the isr 
                nop
        buttonInterrupt: 
            li $a1, 1 #Set $a1 to 1, per the instructions to reset counter 
            li $i1, 0b0011 #Bits used to clear interrupt in status register 
            j endISR #Jump to end of isr 
            nop
    j mainISR #possibly unnecessary isr loop 
    nop
    endISR:
        sw $i1, 4($s1) #clear handled interrupts
        lw $i1, 0($s1) #get the mask register
        ori $i1, $i1, 1 #set Global Interrupt Enable
        restore
        jr $ir
        sw $i1, 0($s1) #resets all interrupts
# ************************************************************

Answer 1

当溢出发生时，计时器会触发。它是32位计时器，所以当您超过值时0xffff ffff您的ISR将被称为。

为0xc8循环进行操作的方法是

li $t7,0xffff ffff
li $t8,0xC8
subu $t7,$t7,$t8
sw $t7,0($t6)