Unable to Enter Debug Mode via Cyclone Rev B If Target is 1.8V

[Designer11]

Hello Everyone,

I'm having a really strange issue between the micro 9S08QE32 and Cyclone Pro Rev B. If the micro is running at 3.3V, the Cyclone is able to enter debug mode without any problem. However, when the micro voltage is at 1.8V (which is within the micro specification) the Cyclone refuses  to enter debug mode. I believe the Cyclone will work with 1.6V to  5V.  Is there any setting on the cyclone i can change to make it works ?

Environment:  CodeWarrior for MCU version: 10.5

Thanks,

Vu

[Designer11 · Accepted solution]

Hi,

Problem solved. The VDD pin 6 on the programing header needs to connect to the micro power supply so that BKGD and RESET lines have a reference voltage. Somehow my cyclone pro B has a 3.2V presents on pin 6 (problem for another day). But the actual solution is the micro WON"T get into debug/programing mode at 1.8VDC. I even tuned the power supply to 1.85V and still no luck. The datasheet said the micro will operate between 1.8V to 3.6VDC. However, the minimum voltage you need is 1.94VDC. I've wasted two days to find this out. 

Thanks,.