The hardware manual of BF54x tells me that GPIO pins are in input mode after reset. Upon my understanding, all of these GPIO pins should be in tri-state if no code sets them as input/output during or after BF powers up. What mode are GPIO pins in if Blackfin is not powered up at all? What is the impedance of GPIO?
The reason why I get this question is the signal connecting to PG6 will drop from high level to low level as long as system powers up except BF. There is 4.7k pull-up resistor (3.3V) connecting to PG6 in system.