USB-6509 I/O Pull-Up/Pull-Down Resistors

The USB-6509 facilitates user-configurable pull-up or pull-down tasks. Each DIO channel is connected to a 100 kΩ resistor and can be pulled high or low using the switch on the USB-6509 back panel.

Using the switch pulls all 96 DIO lines high when set to HIGH or low when set to LOW. If you want to pull some lines low or high, you must understand the nature of the drive current on those lines and adhere to TTL-logic levels.

Use the following examples to understand how to pull a specific line low or high.