For the RS-485 daisy chained serial bus to operate properly, the ends of the bus must be electrically terminated. This electrical termination prevents transmitted signals from being reflected back into the cable and corrupting valid data. However, interior boards in the daisy chain must not have any electrical termination.
To allow a GIO to be placed anywhere in a RS-485 daisy chain, this board includes configurable bus termination that is controlled by two jumper posts at position J6 on the top surface of the board.
When a GIO is placed at either end of a RS-485 daisy chain, the two (2) posts must be jumpered together to terminate the bus. When a GIO is placed at an interior node of a chain, the jumper must be removed. As shipped from the factory, the jumper is installed and the GIO is ready to be connected at either end of a chain.