8-bit MicrocontrollersのトピックRe: Reset Vector

Reset Vector

presto — Thu, 29 May 2008 19:47:18 GMT

Hey,

I'm working with a 8-bit freescale micro and I have heard that it might be possible to use dont cares in your reset vector, is that true? I

I've only heard of it from one source so I wanted to find out if it was possible and if so how do I go about doing it(C or assembly is fine)

Thanks!

Re: Reset Vector

JimDon — Thu, 29 May 2008 22:16:01 GMT

What exactly do you mean by "don't cares". If you mean any value, which is usually what "don't care" means, then no, it must point to your start up code.

If you mean that you don't have address that your self because the project frame work does, then yes, you do not have to do anything for your program to make it to "main" from a reset.

Message Edited by JimDon on 2008-05-29 11:16 AM

Re: Reset Vector

presto — Thu, 29 May 2008 22:30:56 GMT

hey,

My question originates becuase I have a micro that I'm reading in and the reset vector that Im getting is out of valid range for the chip.

i considered big and little endian but even bit flipped the reset vector is invalid.

any ideas why I would be reading in an incorrect reset vector?

The chip I have has code already on it and I'm trying to preserve it.

Re: Reset Vector

JimDon — Thu, 29 May 2008 22:35:26 GMT

What chip is it? Part number?

Re: Reset Vector

denny_george — Mon, 02 Jun 2008 19:10:42 GMT

Hello,

Why would anyone want to read the RESET VECTOR ?

And instead of having don't care value , a dummy ISR address is given normally. Its a good practice from system point of view.

Re: Reset Vector

UK_CF_FAE — Tue, 10 Jun 2008 05:49:43 GMT

Hi Presto,

Welcome to the forum.

So you have a non-specified Freescale 8-bit mcu which you are trying to read to 'preserve' the code, and the reset vector does not make sense?

I can think of many, many reasons why this is the case.

Could the device be secured against intrusive access?

Might this be a RS08 and the 'reset vector' is not where you think it is (it is not at 0xFFFF)

You have an HC08 in Monitor Mode

Before we all expend lots of energy on this problem, can you please provide the following information

1) Please warrant that this is your application that you are trying to preserve, and that you are not trying to reverse engineer anything. I would not want to help you to do that.

2) Please give us either the device part number (if you know it) or the legend printed on the top of the device. All the details from every line. If you do not know the device part number, please see item 1).

3) The mechanism that you are using to read the device. Mono8, BDM, SEM (if it is a SEM, see item 1))

4) For those of us with analytical brains, what address are you reading, and what values are you getting?

Mark