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Forum Index : Microcontroller and PC projects : Loosing seconds when using CPU nn

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piclover
Senior Member

Joined: 14/06/2015
Location: France
Posts: 134

Posted: 07:01am 06 May 2016

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Geoffg said OK, this will be fixed in 5.2 by scaling the timer count to keep as accurate as possible.[/quote]Cool, thanks !

Geoffg said Also, while I was at it I found out how to get 20MHz, 10MHz and 5MHz on the MX470 (cool).[/quote]As an SMD-impaired-old-fart, I don't use the MX470... But cool nonetheless !

[quote]Finally, while talking about clock speeds. You have always been able to overclock a 50MHz spec MX170 to 60MHz. For some reason you must start at 30MHz. Eg:
CPU 30
CPU 60

This is not guaranteed to work but it seems to be OK on most chips

In my experience, while the CPU core does usually work fine at 60MHz on 50MHz MX170 PICs, the (internal) peripherals don't like it at all, and this always ended up, for me, with a crash/restart of the PIC... I don't know whether it is at all possible (I doubt it), but perhaps could the PIC be convinced to run the peripheral bus speed at 50MHz and the core at 60MHz ?...

matherp
Guru

Joined: 11/12/2012
Location: United Kingdom
Posts: 10201

Posted: 07:30am 06 May 2016

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Quote but perhaps could the PIC be convinced to run the peripheral bus speed at 50MHz and the core at 60MHz ?...

Not possible but the chip can do 60/30. Unfortunately this needs quite a lot of work in the firmware as things like the UART are clocked on the peripheral bus. On the MX470 80MHz is the fastest you can do 1:1 after that it is 1:2 so at 100MHz the peripheral bus is actually running at 50MHz. The MX470 firmware copes with this but it would be another increase in firmware size on the mX170 for a speed that isn't within the chips spec.Edited by matherp 2016-05-07

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