AnsweredAssumed Answered

MCF52254 internal pull-up default state

Question asked by Wei Xu on Oct 15, 2018
Latest reply on Oct 19, 2018 by TomE

Hi Team,

One of our project uses MCF52254 PTA2 pin as a PWM output to control the LCD back light, every time when powered up, there is a short pulse at the pin, this will cause a flicker of the back light. I probed the signals, I supposed the pulse is caused by internal pull up.

C1: Reset pin

C2: PTA2(PWM pin)

C3: Another PWM pin with lower pull down resistor

C4: 3.3V MCU supply


I checked the manual, it says the initial state of pull-up is disabled:


But another table in the manual says the initial state of the pull-up is enabled:

So, what is the exat state of the internal pull-up during  power up? How can we disable the internal pull up?  


Thanks and regards!

Wesley Xu