At 10:51 AM 1/27/2004, David Schmidt wrote:
>I'd like to use an SSOP 20 packaged 16F627A in a project.  I have a
>picstart plus, but no programming adapter for an SSOP20.
>I would like to solder the SSOP20 into my PCB and program it "in-circuit"
>using my picstart plus (also I may need to change the
>firmware later to correct for bugs).
>
>- Is the in-circuit programming of the 16F627A the same hookup, voltages
>and algorithm that the picstart plus uses?
>(can I just jumper over the 5 pins needed for in-circuit programming from
>the picstart plus?)
>
>Thanks.  The microchip website didn't list the picstart plus as being able
>to program in-circuit, but I suspect that is just because they don't offer
>a hookup cable.

The PS+ is definitely capable of doing ICSP.  You may need to buffer the
supply voltages and possibly even the data & clock lines, depending upon
what your circuit configuration looks like.

I'll give a specific example: one of our products uses either a 12c508 or a
12f675, depending upon which variant is being produced.  These are built
several hundred at a time with blank chips.  We use a PS+ to program the
chips in circuit: both Vdd & Vpp have active buffers as per Microchip
app-note TB017 and the clock & data lines have the simple 'stoopid' buffers
I described several months ago.  The 'stoopid' buffers are required because
the programming pins have heavy loads (820R) tied permanently to the pins
and the PS+ cannot drive those loads.  Works well.

dwayne

--
Dwayne Reid   <dwayner@planet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
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