I am using a dspic30f4011 controller. I am confused about the oscillator frequency. According to the datasheet, it can support 4 to 10 MHZ. I have 8 MHZ and 11.0529 M HZ crystal oscillator. I know, there are two types of the external oscillator can be connected to the controller. 1. XT which is up to 4 MHZ and other is 4 MHZ to 10 MHZ which is HS type oscillator. I am using this oscillator with dspic30f4011. I don't know this type. It might be HS type as it is with high frequency.

But the problem is that I am not using the external oscillator below 10 MHZ. If I used 110.592 MHZ oscillator, What will happen? should I have to use exact value of external oscillator?

define FCY 18000000 //

define FPWM 4000 //

define DEADTIME (unsigned int)(0.00004* FCY)

define FOSC 11052900 //64MHZ

can you tell me what I have to configure about FCY, FOSC for this crystal oscillator for dspic30f4011?

I am very sorry for this question but I am confused with much more information on the internet.

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  • \$\begingroup\$ You shouldn't get overwhelmed and confused with internet information. All you need is to read the datasheet, ww1.microchip.com/downloads/en/devicedoc/70135C.pdf and understand options for oscillator configurations, to recognize that there are limits if you use PLL or not (you can't use 11 Mhz if you use PLL for example), and properly select configuration mode, see section 21.2. If you can't do this, get info on a proper reference board with code samples, and do EXACTLY as they do. \$\endgroup\$ – Ale..chenski Feb 6 '18 at 23:07
  • \$\begingroup\$ This is all spelled out in the PIC data sheets. They go into nauseating details about overall specs plus individual chapters about each section, including oscillator options, various divider and PLL options, etc. Please read this material in detail. You will find all the answers you need. Note that you may need the master PICdsp data sheets to get some fine details. Search the Microchip PIC website for documents. \$\endgroup\$ – Sparky256 Feb 6 '18 at 23:08

What I read, contradicts your info, perhaps due to versions of datasheet.

Oscillator System VERSION 1 & 2 Page 8 2007
5: XTL – XTL Crystal Oscillator mode (200 kHz-4 MHz crystal).
6: XT – XT Crystal Oscillator mode (4 MHz-10 MHz crystal).
7: HS – HS Crystal Oscillator mode (10 MHz-25 MHz crystal)

Version 2 enables HS mode to the PLL for more Xtal options.

Rule of thumb is you can try XT mode which uses less power and if start problems occur at higher temperatures ( lower CMOS gain) then use HS mode 10~25MHz with HS/2,/3 and PLL x4, x8, x16 options.

EC mode is limited to 0 ~ 40MHz and not 110.592 MHz which must go thru a prescaler if necessary to get below 40MHz AND use a synchronous clock.


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