Appendix B. Terms and Definitions
New BeagleBone users come from backgrounds that vary both technically and geographically. In this appendix, we will go through some terms to help you understand this book and other BeagleBone resources such as the community mailing list:
- Active low/active high: These are different electrical ways of describing a signal. Active high and active low refers to the electrical state a signal is considered to be active. For example, an enable or chip select signal can be described as active high or active low. An active low enable or chip select signal means when the signal is at the electrical value
0(usually 0V), the signal is enabled or the chip is selected. Conversely, an active high enable or chip select signal means when the signal is at the electrical value1(3.3V for the BeagleBone), the signal is enabled or the chip is selected. The opposite state in both cases would mean the chip is not selected. A related concept is tristating. - Altoids tin...
