QG8: Frequency change to ~7966720hz.

[HarrySun]

Hello,

I use illegal instruction,__asm "JMP 0x00", to reset QG8 if certain conditions are met, but after the reset , in the "command" windows of DEBUGGer, a message " Frequency change to ~7966720hz" appears.

the normal frequency showing in the window is 1Mhz and in fact is my qg8 bus frequency.

so why this frequency was changed after this reset by illegal instruction?

if qg6 works alone, will this frequency-changing problem happens ?is this a debugger problem??

I think after reset, the frequency should be set by my initialization code inside mcu, which is 1Mhz.

thansk verybody.

Harry

Message Edited by HarrySun on 2007-03-2807:37 PM

Message Edited by HarrySun on 2007-03-2807:38 PM

[Alban]

Hello,

If you have a Reset, the BDM need to resynchronize.

It tried to synchronized at 8MHz.

What is the (default) value of oscillator ?

Alban.

[HarrySun]

Alban,

I always appreciate your prompt reply.

I use internal clock source set to 1MHZ bus frequency,no ouside oscillator.

so why it's so?I still don't understand.

thansk

[jarin]

Default ICS configuration (for QG8) after reset is FEI mode (FLL engaged internal reference). Internal reference runs on approx. 32 kHz, reset default divider (RDIV in ICSC1) is 1, then *512 in FLL gives slightly more than 16MHz. Default frequency divider (BDIV in ICSC2) is 2, this gives about 8 MHz. Because of normal deviation of untrimmed internal oscillator initial (untrimmed) output frequency can vary, but your 7,96MHz is perfectly OK.

Note this is default configuration and this MCU starts after reset in this mode and with this frequency.

[peg]

Hi Harry,

Just about to answer and jarin beat me to it.

Following on from his answer:

So the QG8 always runs at approx. 8MHz for a short while until it gets to the part of your intialisation code that changes it to something else. Of course this occurs with or without BDM debugger attached. You just don't notice it.

The values shown by the debugger are correct (in this case).

[HarrySun]

Hello,Jarin and Peg,

your answers are really crystal clear...thanks a million.

now one more question is why the frequency cann't be changed back to 1mhz  after its' reset?

I noticed:

in normal mode, the Command window shows about 1mhz frequency; then after an illegal reset,it shows 8Mhz frequncy and never shows 1mhz afterwards, the Mcu works as usual, though(but I am not sure if the timing is still right).

so after reset ,in the command window,it should first show 8MHZ, then shows the frequency I set,is this correct??

thanks

Message Edited by HarrySun on 2007-03-2901:28 PM

[peg]

Hi Harry,

Does the device continue to run at 1MHz and you are just concerned that the debugger is not advising you of the last frequency change?

If this is the case, I would not be too concerned. You will notice in my last post i said (in this case), the reason for this is that I do not place much faith in this indication from P&E, it often appears wrongly or not at all.

For me if I see a change when I don't expect it I assume a reset occurred, I don't try to read any more into it than that.