Which microcontroller and what speed

Thread Starter


Joined Oct 26, 2008
Hi everyone, I've got some basic questions before I start looking around and purchasing. I have some projects I want to get started on, and I was wondering if anyone would recommend a good 18-series chip from microchip. I'm ordering a pickit2 as my programmer also, so anything that is compatible with that.

Also how do you go about designing the clock that runs on the chip? I've been kind of confused about this and couldn't really find any info on google when searching. I figure I can just buy a resonator, but what frequency should I buy? I think it depends on which chip you pick out, but I'm kind of lost. Any website or explanation that can point me in the right direction would be awesome. thanks again
Once you have decided on the 18-series parts, the rest is up to your memory and i/o needs for the chip. Microchip has a table on their website which compares all of the parts in the series for memory, i/o, clock speed, ...

All of these things will depend on your application. If you are not sure, pick a big one and then optimize later if you have the time or need.


Joined Aug 15, 2007
I got the impression that the O/P is confused about the on-chip clock: "Also how do you go about designing the clock that runs on the chip?"

If that is so, then the basic answer is "it just runs" at the frequency determined by Microchip. If a different freq. is needed, then an external crystal may be needed. You'll need to check the data sheet for the chip to find out how to tell the micro that its clock source is external.



Joined Aug 3, 2007
When you are a beginner, I think it's best to get the most popular microcontroller(s), because you can find the most help on it.

For PIC18, the most popular is PIC18F4550 (I use this one also). This is a 12 MIPS, 48 MHz clock microcontroller.
See this: http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010300

Even though it says it's a 48 MHz clock, I used a 24 MHz oscillator with multiplier setting ON, so that it still runs at 48 MHz.

So, in other words, you can use either a 24 MHz oscillator or 48MHz oscillator.