On Mon, April 14, 2014 10:04 pm, Larry Bradley wrote:
> Just got one the other day.
>
> They use the internal RC oscillator. The 24F chip has a basic 8 mHz
> clock, rated at 0.25% accuracy, I think. There is an on-board PLL for
> the USB port that gets you higher clock rates.

The internal FRC on the PIC24FJ64GB002 is +1%, -1.25% max, 0.25% typical.
This usually isn't good enough for asynchronous comms- while it may work
*most* of the time, you need to be aware that it could get out of spec.
The rule of thumb I use is that the baud rate error could be 10x the clock
error (since there are 10 bit-times in a standard N81 serial stream).

In general, I don't trust internal oscillators in asynchronous comms- too
much of a chance for data errors. If reliable comms are important, use an
external clock source (crystal, resonator, or oscillator) or synchronous
comms, like I2C or SPI.

Matt Bennett
Just outside of Austin, TX
30.51,-97.91

The views I express are my own, not that of my employer, a large
multinational corporation that you are familiar with.
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