Paper sheet handling apparatus and method of configuring pld in paper sheet handling apparatus

A method of configuring a programmable logic device (PLD) in a paper sheet handling apparatus including a plurality of mechanical units including a paper sheet handling unit, the plurality of mechanical units each comprising

• a processor,
• a PLD controlled by the processor,
• a first mechanical module including a first mechanical element controlled by the PLD, and
• an interface that connects a second mechanical module including a second mechanical element, wherein
• when the processor detects connection of the second mechanical module via the interface, the processor reads, from a second storage included in the second mechanical module, the second storage storing second firmware of the processor configured to control the first mechanical element and the second mechanical element and second data for use in configuring a logic circuit of the PLD configured to control the first mechanical element and the second mechanical element, the second firmware to load the second firmware onto the processor, and the processor reads the second data from the second storage to configure the PLD.