new example

+IRQ0:
+  # set IP for process B in its first stack frame
+  set  R1 @intr1B  # top (empty)
+  dec  R1          # where interrupt mask is saved
+  set  R0 0xFFFF   # mask
+  save R0 R1
+  dec  R1          # where IP is saved
+  set  R0 @processB
+  save R0 R1       # assign it to @processB
+  # start process A
+  set  SP @intr0A
+  set  R0 @processA
+  jmp  R0
+
+# which process is running
+# - 0 => process A
+# - 1 => process B
+current:
+  = 0
+
+IRQ2:
+  # check which process is running
+  set  R0 @current
+  load R0 R1
+  set  R2 @switchB
+  jz   R1 R2
+  switchA:  # switch to process A
+    dec R1
+    set SP @intr1A
+    set R3 @end
+    jmp R3
+  switchB:  # switch to process B
+    inc R1
+    set SP @intr1B
+  end:  # update the running process
+    save R1 R0
+    iret
+
+# code for process A: make R0 blink (AAAA/4444)
+processA:
+  set R0 0xAAAA
+  set R0 0x4444
+  set R1 @processA
+  jmp R1
+
+# code for process B: make R0 blink (BBBB/8888)
+processB:
+  set R0 0xBBBB
+  set R0 0x8888
+  set R1 @processB
+  jmp R1
+
+# stack for process A
+intr0A:  # frame for IRQ0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+intr1A:  # one more frame
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+intr2A:  # one last frame
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+
+# stack for process B
+intr0B: # frame for IRQ0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+intr1B: # one more frame
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+intr2B: # one last frame
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0
+  = 0

+top:
+  = 0
+
+IRQ0:
+  intr 4
+  set  R4 @top
+  load R4 R0
+  sub  R0 SP
+  halt
+
+IRQ4:
+  set R0 @top
+  save SP R0
+  iret
\ No newline at end of file