Setup stack pointer and runtime priority

programs/assignment2isr.prog

@@ -0,0 +1,96 @@
+reset:
+    br always >main
+    nop
+hardfault:
+    reti
+    nop
+memfault:
+    reti
+    nop
+
+.align
+led_addr: .word 0x000F0000
+switches_addr: .word 0x000F0004
+dmem_start_addr: .word 0x00000400
+dmem_end_addr: .word 0x000004FF
+base_prescaler: .word 0x1
+priority_mask: .word 0xFFFFFF03
+
+main:
+    // Initialize stack pointer to the end of the data memory
+    ldr r12, >dmem_end_addr
+
+    // Set runtime priority
+    ldr r0, >priority_mask
+    and r14, r0, r14
+
+    ldr r0,>led_addr    //LED addr
+    addi r6,8        //outer counter top
+    clr r7            //wait counter
+    ldr r8,>base_prescaler
+
+out_loop:
+    clr r1
+    st08 r0,r1
+    call >wait_prescaled
+    nop
+
+fill:
+    lsh r1,r1,1
+    addi r1,1
+    st08 r0,r1
+    call >wait_prescaled
+    nop
+
+    addi r5,1
+    cmp neq r5,r6
+    br true >fill
+    nop
+    clr r5
+
+flush:
+    lsh r1,r1,1
+    st08 r0,r1
+    call >wait_prescaled
+    nop
+
+    addi r5,1
+    cmp neq r5,r6
+    br true >flush
+    nop
+    clr r5
+    br always >out_loop
+    nop
+
+wait_prescaled:
+    // Load value from the switches
+    ldr r11,  >switches_addr
+    ld32 r9, r11
+    addi r9, 1
+
+    clr r11
+    add r11, r13, r11 // save link register
+
+    clr r10
+inc_j:
+    call >wait
+    cmp neq r10,r9
+    br true >inc_j
+    addi r10,1
+
+    clr r13
+    add r13, r13, r11 // restore link register
+
+    ret
+    nop
+
+
+//subroutine to iterate until counter overflow
+wait:
+    clr r7                //inititalize inner counter
+inc_i:
+    cmp neq r7,r8
+    br true >inc_i        //if i=cnt_top
+    addi r7,1
+    ret                    //else
+    nop