ComputerCraft turtle program - mob grinder

local lastState = false
local dropInterval = 0

while 1 do
    if redstone.testBundledInput("top", 1) == true then
        if lastState == false then
            lastState = true
        end
        if dropInterval >= 1200 then
            dropInterval = 0
            for i = 1, 16, 1 do
                turtle.select(i)
                turtle.drop()
            end
        else
            dropInterval = dropInterval + 1
        end
        turtle.attack()
        sleep(0.1)
    else
        if lastState == true then
            for i = 1, 16, 1 do
                turtle.select(i)
                turtle.drop()
            end
            lastState = false
        end
        sleep(10)
    end
end