HCS08QG8 clock question

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HCS08QG8 clock question

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airswit
Contributor III
Hi everyone,

I would like to run the processor at a very slow clock speed, for low power. My question is: If i set the internal clock as the low power oscillator (32kHz), can i still re-program the chip later?
I mean, i tried that setting in a bean, and it gave a warning that the clock cannot be below 150kHz in order to program the flash rom.
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Wings
Contributor I
airswit - You're not going to enjoy debugging your QG8 with such a slow clock (see my post about Slo-Mo Debug a few posts down) if you're using P&E's debugger.

Also, don't forget that your BUSCLK will be 1/2 the internal clock oscillator, or around 16KHz, not 32.

As far as programming the flash when you're hooked up to a debugger tool, your chosen clock speed won't matter. It will program just fine no matter what. The 150KHz lower speed limit is for your app programming its own flash.
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airswit
Contributor III
alright, thanks everyone...i will see if this works later on. the debug thing *should* not be a problem, since i know that the code works at the full clock speed, and i am using the mtim to use timing, which i have set up to use the xosc anyhow. i just think that if i disable the FLL and slow down the core clock, I should see near the same functionality with lower power consumption. The system i am implementing is not very complicated!

Thanks for the advice!
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Alban
Senior Contributor II
Yo,
 
The internal charge pump requires the chip to work above the specified frequency to ensure the cells are properly programmed.
 
You have a lot of possibilities here. If you are talking about your embedded software saving data in Flash, you will just need to icrease the bus frequency temporarily when you want to program.
 
You can still reprogram the chip later... But not at a so low frequency.
 
Alban.
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