Shereef Sayed

Problem w/ PORTA & B after RESET

Discussion created by Shereef Sayed on Feb 7, 2007
Latest reply on Feb 9, 2007 by Daniel Lundin
I am using the 9S12XDP512 from TechArts and connecting 3 Lynxmotion Tracker Sensors to PORTA[7:5], PORTA[2:0], and PORTB[7:5]. The Tracker Sensor outputs HI for WHITE light, and LO for BLACK light. I have configured the Data Direction registers for PORTA & B (i.e. DDRA = 0x14; DDRB = 0x1F; ). Also, the MCU provides the +5VDC to power the sensors.
The problem occurs when I switch the controller to 'Run' and press the 'Reset' button. Nothing happens, until I place a WHITE sheet of paper under the PORTA sensors. Only then does the program execute. Why does my program require an external event to start?
Thanks for your help.