Updated the instruction set and mapped out the opcodes as well as wrote a sample program to see if the ISA was complete enough to build a trivial program.

misc/another_test.asm

@@ -1,3 +1,40 @@
-some_stub:
-    pop r8
-    jmp [r8] ;return to the calling code.
+.db MAX_MEM 0xFFFF
+.db VIDEO_MEM 0xF37F
+.db MAX_LENGTH MAX_MEM - MAX_LENGTH
+.db MSG "Hello, World!", 0
+
+_start:
+    copy r1, MSG ; Pointer into r1
+    copy r8, VIDEO_MEM
+    call strlen
+    copy r1, MSG
+    cmp r2, 0
+    je _end
+    cmp r2, MAX_LENGTH
+    jg _end
+draw_loop:
+    copy byte [r8], [r1]
+    inc r1
+    inc r8
+    dec r2
+    cmp r2, 0
+    je _end
+    jmp draw_loop
+_end:
+    jmp _end
+
+; Returns the length of a NULL terminated string
+; Arguments: R1 - Pointer to the string
+; Returns: R2 - Contains the length of the string
+strlen:
+    copy r2, 0 ; length
+    cmp [r1], 0
+    je end ;The string is zero length
+loop:
+    inc r1
+    cmp [r1], 0
+    je end
+    inc r2
+    jmp loop
+end:
+    ret