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<div class="moz-cite-prefix">No JTAG - the chips are flashed with a
bootloader, which is only active on chip reset. Everything is
programmed via a USB-to-serial thingy.<br>
<br>
On 27/07/14 17:25, Steve Kerrison wrote:<br>
</div>
<blockquote
cite="mid:CANxPWH78iD_Odt_9f+REHOLnPDOA26oGVBzmsY8sNGZ9b9x1cA@mail.gmail.com"
type="cite">
<p dir="ltr">Is JTAG connected during test runs? Interested to
know how much difference that makes, although it should be
constant thus irrelevant.</p>
<div class="gmail_quote">On 27 Jul 2014 17:13, "James Pallister"
<<a moz-do-not-send="true"
href="mailto:James.Pallister@bristol.ac.uk">James.Pallister@bristol.ac.uk</a>>
wrote:<br type="attribution">
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000"> Hi All,<br>
<br>
Some preliminary findings on variations in the ATMEGA328
chips.<br>
<br>
I've tested 28 chips. For each chip 9 tests were ran:<br>
<br>
<table border="1" cellpadding="2" cellspacing="2"
width="733" height="58">
<tbody>
<tr>
<td valign="top">flash0<br>
</td>
<td valign="top">Test the area of flash 0x0800-0x0810<br>
</td>
</tr>
<tr>
<td valign="top">flash1<br>
</td>
<td valign="top">Test the area of flash 0x080C-0x081C</td>
</tr>
<tr>
<td valign="top">flash2<br>
</td>
<td valign="top">Test the area of flash 0x08FC-0x090C</td>
</tr>
<tr>
<td valign="top">flash3<br>
</td>
<td valign="top">Test the area of flash 0x0FFC-0x100C</td>
</tr>
<tr>
<td valign="top">ram0<br>
</td>
<td valign="top">Repeatedly access 0x0000 - 0x0020<br>
</td>
</tr>
<tr>
<td valign="top">ram1<br>
</td>
<td valign="top">Repeatedly access 0xF007 - 0xF017<br>
</td>
</tr>
<tr>
<td valign="top">alu<br>
</td>
<td valign="top">Perform combinations of mul, fmul,
inc and dec<br>
</td>
</tr>
<tr>
<td valign="top">nop<br>
</td>
<td valign="top">Lots of nops<br>
</td>
</tr>
<tr>
<td valign="top">branch<br>
</td>
<td valign="top">Repeatedly branch randomly in low
flash<br>
</td>
</tr>
</tbody>
</table>
<br>
Each test was run 8 times, and outliers excluded. All were
run in the same harness, with the same crystal, resistors,
etc.<br>
<br>
Results across each test. These show the distributions of
the measurements taken, where the distribution consists of
the 28 chips.<br>
<img src="cid:part2.07000909.03070101@bristol.ac.uk" alt=""><br>
<br>
From the first graph: there is a significant different, even
on a day to day basis. I'm not sure what causes this - I'd
expect the power to be lower at lower temperatures, which we
don't see.<br>
<br>
For each chip:<br>
<img src="cid:part3.05040509.03000009@bristol.ac.uk" alt=""><br>
Mean power for each chip:<br>
<img src="cid:part4.03030408.08020707@bristol.ac.uk" alt=""><br>
<br>
<br>
The average power changes quite a lot, going from < 80mW
to > 100mW. In almost all cases, the average power was
higher on Saturday - not sure why this is, the temperature
difference was only 3-4 degrees (and I'd expect the
temperature to go down with lower temperature).<br>
<br>
The chips tend to vary as a whole, e.g. rather than the ALU
varying significantly in one part rather than another. The
following graph marks the average power for each test,
divided by test type (different color/marker combinations)
per chip. This should allow hopefully allow us to do a
calibration run first.<br>
<img src="cid:part5.05050804.02090304@bristol.ac.uk" alt=""><br>
Legend for the above graph:<br>
<table border="1" cellpadding="2" cellspacing="2"
width="318" height="58">
<tbody>
<tr>
<td valign="top">Blue cross<br>
</td>
<td valign="top">ram1<br>
</td>
</tr>
<tr>
<td valign="top">Red star<br>
</td>
<td valign="top">ram0<br>
</td>
</tr>
<tr>
<td valign="top">Green plus<br>
</td>
<td valign="top">alu<br>
</td>
</tr>
<tr>
<td valign="top">Black plus<br>
</td>
<td valign="top">flash3<br>
</td>
</tr>
<tr>
<td valign="top">Green cross<br>
</td>
<td valign="top">flash2<br>
</td>
</tr>
<tr>
<td valign="top">Blue star<br>
</td>
<td valign="top">flash1<br>
</td>
</tr>
<tr>
<td valign="top">Red plus<br>
</td>
<td valign="top">flash0<br>
</td>
</tr>
<tr>
<td valign="top">Black star<br>
</td>
<td valign="top">nop<br>
</td>
</tr>
</tbody>
</table>
<br>
<br>
Any thoughts / ideas for more tests are welcome.<br>
<br>
<br>
James<br>
</div>
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