8-bit Microcontrollers中的主题 Re: Uninitialized Memory

Uninitialized Memory

DavidoBG — Thu, 20 Nov 2008 16:50:37 GMT

i use Real time Debugger to debug my program.

I can see in my flash part memory some "uuuuu" uninitialized octect when it is not use. But it is not possible that this octect is initialized with 0xFF per default.

In fact, i think, before write data in flash, all flash was erase (0xFF) in all octect? No?

Because, when i try to read a page of 512 bytes, sometime all bytes is not use so uninitialized. My program halted!!!!

David

Re: Uninitialized Memory

austinjoe — Fri, 21 Nov 2008 00:50:18 GMT

1> Please make sure that the FLASH that you try to access is in fact exsit on the device that you're working on.

2> When build your s-record, fill the unused FLASH with either 0xFF or opcode for NOP to help you catch any run time error like program counter PC goes nowhere.

Re: Uninitialized Memory

Ake — Fri, 21 Nov 2008 16:22:40 GMT

Hi,

I have some difficulty in understanding what you want to do, and what you are doing.

But when you say that you get "uuuuu" figures, it means that you are not using any real hardware.

You are using the software simulator which runs your code on you PC. No MCU is involved.

This simulator does not simulate everything on a PC. Eg you cannot run a Flash EPROM erase/program program and check that it works.

Please tell us what kind of MCU you are using, and then I can check if I have got the kind of program that you need!

Regards,

Ake

Re: Uninitialized Memory

CrasyCat — Mon, 24 Nov 2008 18:48:06 GMT

Hello

Can you please check what is the name of the menu specified after the Run menu in the menu bar?

I am suspecting that you are currently debugging in full chip simulator instead of using run time debugger. "uu" is only displayed within the simulator for memory cell, which have not been initialized yet.

CrasyCat

Re: Uninitialized Memory

DavidoBG — Tue, 25 Nov 2008 23:53:32 GMT

Yes full chip simulation!!! Thanks you for yours help

David

Re: Uninitialized Memory

bigmac — Wed, 26 Nov 2008 09:30:02 GMT

Hello David,

The program halt because of uninitialised memory is a "quirk" of full chip simulation (FCS) only. It will not occur when using the actual silicon, where unprogrammed flash will read as 0xFF, as you expected.

To test sections of code under FCS, it is sometimes necessary to provide additional initialisation that would be unnecessary for the final code. However, using FCS, it is not possible to completely test any code that programs data to flash memory. This must be tested on the actual device.

Regards,
Mac