Hi there, Olin.

I struggled with the decision to make my comments public, but your 
reply to my most recent message to you suggests that public might be 
the way to go:

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From: "Olin Lathrop" <olin_piclist@embedinc.com>
To: "Dwayne Reid" <dwayner@planet.eon.net>
References: <327333.46946.qm@web50506.mail.re2.yahoo.com> 
<4B9146FE.8040608@sbcglobal.net> <4B915142.2040104@sbcglobal.net> 
<698781.27456.qm@web50503.mail.re2.yahoo.com> 
<4B91BDAD.10804@sbcglobal.net> 
<568545.81976.qm@web50503.mail.re2.yahoo.com> <4B93223B
Subject: Re: [PIC] measuring 220V mains
Date: Sat, 20 Mar 2010 10:06:12 -0500
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 > I don't want to pursue this very far,

I just realized this is a private message, so there is no need for me 
to respond at all.

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At 07:41 AM 3/21/2010, Olin Lathrop wrote:
>Josh Koffman wrote:
> > Hi all. I've been looking at some of Andrew Warren's code at
> > http://reocities.com/SiliconValley/2499/code.html
>
>I quick look shows this is really bad* code and nobody should be using it as
>a example.  It does prove (assuming it works), that the problem can be
>easily solved.  Start from the problem definition and write your own code.
>
>* Two immediately obvious problems.  First, EQU is apparently used to define
>constants that are later used as the addresses of memory locations.  Second,
>there is not a single comment in sight.  With two major irresponsibilities
>in such a small code snippet, you can't trust anything the author has to
>say.

The blanket statement you made above is rather short-sighted and 
completely un-called for.

I'll make two observations:

1) The code that Andrew Warren wrote was most likely written BEFORE 
MPLAB had the capability of generating re-locatable code.  EQU was 
THE way that you specified memory locations.  CBLOCK was not 
available - the directive did not exist.

I can send to you a copy of the early assembler that Microchip gave 
to me when I first started with PICs if you don't already have a 
copy.  Look all you like - no ability to generate relocatable code.


2) Andy doesn't comment all of his code.  That doesn't mean that its 
bad code.  In fact, it doesn't mean anything at all except that he 
didn't comment his code.


I'm jumping to Andy's defence for a couple of reasons: he's not 
around to defend himself and he has written some extremely good code 
- and shared it.

I'll leave you with this thought: it was Andrew Warren who first told 
Microchip (and the world) how to safely save context when responding 
to an interrupt.  That is: no one at Microchip could figure out how 
to save context without trashing W.  Andrew was the person who came 
up the idea (swapf w) - and did it on the spur of the moment while in 
the midst of a conversation on the old Compuserve BBS.

I could say much more but I'd be risking moderation <grin>.

dwayne

-- 
Dwayne Reid   <dwayner@planet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax
www.trinity-electronics.com
Custom Electronics Design and Manufacturing

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