2.4.9.3 Signal Terminations

Careful attention should be paid to any notes in the device-specific data sheet regarding the correct termination of pins. In particular, make sure to follow any instructions regarding termination instructions for reserved pins. Also, there are often pins that have special significance at the time the device reset is released. Often these are documented with something like "do not oppose this pin at reset" meaning that if there is an internal pullup or pulldown on that pin, you should not drive that pin in the opposite direction at reset. This would include not putting an opposing pullup/pulldown and also making sure that anything connected to that pin does not drive the pin opposite the intended direction.

Pay close attention to how any unused pin is terminated. Frequently, pins will default to an input state. If left floating, they can pick up noise and toggle at a high frequency. This can cause significant unwanted current consumption. Unused pins should be checked to see if they can be configured through software as outputs so they are not floating. If there is an internal pull-up/down you should configure the level of the output (high/low) to match the pull-up/down for lowest current consumption.