On Mon, 2005-03-28 at 07:27 -0600, michael brown wrote:
> Is it just me, or does it seem like the documentation writers are going
> downhill?  It just seems like the older datasheets were more clear and
> less ambiguous.  I've even seen obvious errors (like the max spec for
> something being less than the typical) and sample code for a peripheral
> that doesn't work (like Howard H recently experienced).

I don't think it's just you.

Another example that I once hit is this: what is the speed of the
internal oscilator on the dsPIC?

If you check the datasheet there are a few places where the speed is
alluded to. For example in the 4011 datasheet:

In table 21-1 (oscillator operating modes): FRC 8MHz internal RC
oscillator (with an odd 7.5MHz for the 16X PLL, I thought that was just
a typo).

In section 21.2.5 (Fast RC Oscillator) it says 8MHz nominal.

Table 24-5: FRC (~2MIPS)

So, you would THINK that the FRC runs at 8MHz (thereabouts).

Well, imagine my surprise when I do some RS232 and nothing is working
right. A check with the scope shows the bits are longer then expected.

I fiddle and fiddle, finally getting the bit time correct. Doing some
reverse calculation I find that the PIC appears to be actually running
at about 7.4MHz. Odd, my 2011 runs at almost exactly 8MHz, as does a
6010 (I think, could be a 6012, can't remember) I had...

So, going to the "accuracy" section of the datasheet (thinking the RC in
the dsPIC is horribly out of whack) I find this table:

Table 24-13: Oscillator Frequency - FRC - typical: 7.3728MHz??!??!?

Of course, some might say it's my fault, I should have checked the WHOLE
datasheet, and they'd be right in a small way. But come on, something
like that is just incredible.
 

-----------------------------
Herbert's PIC Stuff:
http://repatch.dyndns.org:8383/pic_stuff/

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