-- you can change the input/output redstone sides to:
-- top,bottom,left,right,front,back
local tArgs = {...}
pulseLength = tArgs[1] -- In ticks
clockSpeed = tArgs[2] -- In ticks, remember 20 ticks a second

while true do
    while not rs.getInput("bottom") do -- Remove "not" if you want to enable the clock when supplying a signal
        rs.setOutput("top", true)
        sleep(pulseLength / 20)
        rs.setOutput("top", false)
        sleep((clockSpeed - pulseLength) / 20)
    end
    event = os.pullEvent("redstone")
end