A method for designing a system on a programmable logic device includes implementing a first network of logic elements and a second network of LEs with a combined network of LEs that performs a same functionality but utilizes a fewer number of LEs. The shutter drawing portion is swingable in the width direction of the arcuate guide wall portion, and thus occurrence of component force for inclining the shutter main body due to the pulling of the shutter drawing portion can be suppressed. The first logic device generates second data for the received data frame. The engaging cylinder is coupled to the threaded attaching portion.