K8055 OpenDevice(x) and SetCurrentDevice(x) difference

What is the difference between the commands OpenDevice(x) and SetCurrentDevice(x)? In order to access multiple K8055 boards, do I need to open each device (board) before reading and writing data and then closing the device, or can I just “open” all the devices and then just use the SetCurrentDevice to access the different cards?

I access the different cards numerous times throughout the program and I feel like there has to be a better way than constantly opening and closing each device.

Just use SetCurrentDevice(x) to jump between the cards.