class done

lab7interrupts/Src/delay.s

@@ -0,0 +1,59 @@
+# delay.s
+# Trevor Barnes
+# CE2801-031
+# Description: A file for handling delay routines
+
+.syntax unified
+.cpu cortex-m4
+.thumb
+.section .text
+
+.global msDelay
+# A subroutine to create a delay of a certain number of milliseconds
+# Input: 
+#       r0: Length of delay (ms)
+msDelay:
+
+    push {r1,r2,r3,lr}
+    mov r3,r0
+ms_delay:
+	# 250 iterations = 1/16 of a millisecond
+    mov r2, #0x10
+# Loop 16 times
+1:
+	# 250
+	mov r1, #0xFA
+# Loop 250 times
+2:
+    sub r1, #1
+    cmp r1, #0
+    bne 2b
+
+    sub r2, #1
+    cmp r2, #0
+    bne 1b
+
+	sub r0, #1
+	cmp r0, #0
+    bne ms_delay
+
+    mov r0,r3
+    pop {r1,r2,r3,pc}
+
+.global usDelay
+# about r1 mircoseonds
+usDelay:
+	# stack
+	push {lr}
+
+	lsl r1, r1, #3
+
+1:
+	sub r1, r1, #1
+    cmp r1, #0
+	bne 1b
+
+	# return
+	pop {pc}
+
+