Other NXP ProductsのトピックRe: 56F805 Pins During Reset

56F805 Pins During Reset

DrJoe047 — Sun, 21 Oct 2007 23:37:45 GMT

My prototype boards are about a year old - they are using:
MPN: DSP56F805FV80,
LOT: CN13700B01
DTE: 0430

Per the documentation here when the DSP56F805 goes into "Reset State" these pins are supposed to become "Tri-State Input" or "inputs"
GPIOE2
GPIOE3
GPIOD0
GPIOD1
GPIOD2
GPIOD3
GPIOD4
GPIOD5
TC1

When I pull RESET and TRST low, the device is supposed to go into Reset State.

BUT...

...All the outputs are going to 2.5V (high).

What can I be doing wrong?

This is a huge safety issue for my robot design. I cannot go forward if this cannot be addressed in some way. Please Help.

Joe J.
--
Joseph M. Johnson, Ph.D., P.E.
Chief Technologist, Co-Founder
Robotic Amusements, Inc

Re: 56F805 Pins During Reset

william_jiang — Fri, 30 Nov 2007 18:39:32 GMT

How do you connect these pins? These pins may have internal pullups enabled during reset (refer to the attached picture excerpted from 56F801-807 User's Manual).

Re: 56F805 Pins During Reset

DrJoe047 — Fri, 30 Nov 2007 22:01:56 GMT

Thanks for the response.

These pins go to a relay driver (ULN2803) which has internal pull downs (10KOhm I think I don't have the data sheet handy). Even with the internal pull downs, the pins stayed HI (approx 2.5V).

I have to give it to Freescale on this, they did a good job getting back to me. Long story short, it is just as you say, they have internal resistors that kick in during reset.

They told me to just use a lower value pull down to ground. They suggested 5KOhm. It did the trick.

Thanks for the help.

Joe J.

Message Edited by DrJoe047 on 2007-11-30 02:02 PM