Multi-port timer (for minetest luacontroller)

if event.type == "program" then
  mem.a = 1 -- export loop
  mem.b = 50 -- grind loop
  -- mem.c = 100 -- don't remember what this was, but obviously I disabled it
  mem.c = nil
  mem.d = 20 -- smelt loop
elseif event.type == "interrupt" then
  for name, timing in pairs(mem) do
    if event.iid % timing == 0 then
      port[name] = not pin[name]
    else
      port[name] = false
    end
  end
end
interrupt(1, event.iid and (event.iid + 1) or 0)