San Francisco State University

ENGR 478

ENGR 478 Homework 3 Due: Sunday 3/11, 11:55pm on iLearn Name: Student ID: Student Email: I certify that I did not copy the answers to this homework and did not let anyone copy my answers (sign): Preparation: Review Lectures 5, 6, 7, and 8 Question 1 Consider the following interfacing system. Port PA1 is an input port connected with an external switch. PB1 is an output port connected with an external LED. Given the signal of PA1 and PB1, and the behaviors of the switch and the LED shown in Figure 1, the switch interface and the LED interface are , respectively. Put the answer in the box. A. positive logic and negative logic B. positive logic and positive logic C. negative logic and negative logic D. negative logic and positive logic Figure 1. PA1, PB1 signals and the corresponding behaviors of the switch and the LED