CODEWITHSUNDEEP
assemblyarm
DeMilwaukee
DeMilwaukee

Reputation: 39

Assembly Language Led On/Off

I am trying to design a program that the on board LEDs flash every second. So all LEDs on FPGA board on for 1 sec and then off for 1 sec. I was recommended to use interval timer or interrupt service routine to measure the period of one second.

DE-10 NANO

I came up with this solution but does not work. I am not asking you to do my homework, just looking for some advice/tips.

Thanks in advance.

Here is my code so far :

.include    "address_map_arm.s" 

.text        /* executable code follows */
.global     _start 
_start:                         
    LDR     R2, =LED_BASE   // base address of LED lights
    LDR     R3, =LED_BASE   // LED base address
    LDR     R0, =TIMER_BASE          // base address
    LDR     R6, [R2]        // load pattern for LED displays
    STR     R6, [R3]        // store to LEDs
    

DISPLAY:                     
    STR     R6, [R2]        // load SW switches

timer:
        MOV     R0, #0                      // used to stop the timer
        STR     R1, [R0, #0x8]              // write to timer control register
        LDR     R1, =100000000              // period = 1/(100 MHz) x (100 x 10^6)
                                            // = 1 sec
        STR     R1, [R0]                    // write to timer load register
        MOV     R1, #0b111                  // int mask = 1, mode = 1, enable = 1
        STR     R1, [R0, #0x8]              // write to timer control register
        BX      LR      


RESET:

    B       DISPLAY

Upvotes: 1

Views: 2471

Answers (1)

Elliot Alderson
Elliot Alderson

Reputation: 648

It looks like your intention is to read the state of the switches and then display that pattern on the LEDs.

However, if you look at your first two instructions you are loading the base address for the LEDs twice and you never load the base address for the switches. So what your code actually does is read the state of the LEDs and then write that back out to the LEDs. Even if the code is running properly, you will never see any change in the LEDs.

Furthermore, to get the state of the switches you need to use an LDR instead of an STR.

Upvotes: 2

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