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nuckolls.bob(at)cox.net
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 Posted: Thu Sep 18, 2008 7:36 am Post subject: Brad's reply on P-lead switch functionality |
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Received a reply from Brad on functionality of the p-lead switch
in Emag products:
"Grounding the p-lead 1) sends a status signal to the processor (telling it
to stop firing), and 2) disables the driver chips (so they can't fire)."
Bob . . .
----------------------------------------
At 12:19 PM 9/16/2008 -0400, you wrote:
>
><simon(at)synchronousdesign.com>
>
>Jeff, although a good point to bring up, I highly doubt that such an
>important function would go to the microprocessor, except as a status
input.
>Surely it would go to a hard wired shut off circuit outside the micro
>to guarantee outside control without software being involved. If it
>didn't, it would be a major design error. However, all of these
>details are most likely proprietary data, and only Emagair would know.
>
>Simon
--------------------------------------
>Subject: Re: E-Mag P-Mag Safety info - Referenced
>msg from Mr. Cotner
>
>
>
>Any possibility that grounding the P-Lead would have no effect if the
>microcontroller was way too busy handling strangely timed interrupts
>due to the timing sensor bouncing around ? That would depend on
>whether the P-Lead is a standard input read by the microcontroller, or
>goes directly to some circuitry that shuts off the spark outputs.
>Anyone know how the circuirty is designed ?
>
>Jeff Page
>Dream Aircraft Tundra #10
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mrspudandcompany(at)veriz
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| Posted: Thu Sep 18, 2008 8:30 am Post subject: Brad's reply on P-lead switch functionality |
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<nuckolls.bob(at)cox.net>
Received a reply from Brad on functionality of the p-lead switch
in Emag products:
"Grounding the p-lead 1) sends a status signal to the processor (telling it
to stop firing), and 2) disables the driver chips (so they can't fire)."
Bob . . .
Is the driver chip disable signal a "hard wired" signal to the drivers, or
is it a signal derived through the processor? It could be a problem if it
is through the processor, and the processor gets hung up by some inputs with
errors.
Roger
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simon(at)synchronousdesig
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| Posted: Thu Sep 18, 2008 9:22 am Post subject: Brad's reply on P-lead switch functionality |
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Thank you, Bob, for publicly responding. This redundant method of shutting
off the fire signal is a good and proven way of doing it, i.e. better than
simply shutting off the drivers as I said below.
Now the only question is why Marc Zeitlin's engine didn't quit firing? He
claims he tried to shut it off and the P-Lead was connected. Could there
have been an intermittent open in his wiring or possibly a problem in the
PMag electronics, possibly related to temperature or vibration?
Simon
Copyright 2008
--
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dale.r(at)cox.net
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| Posted: Thu Sep 18, 2008 6:45 pm Post subject: Brad's reply on P-lead switch functionality |
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Robert L. Nuckolls, III wrote:
| Quote: |
<nuckolls.bob(at)cox.net>
Received a reply from Brad on functionality of the p-lead switch
in Emag products:
"Grounding the p-lead 1) sends a status signal to the processor
(telling it
to stop firing), and 2) disables the driver chips (so they can't fire)."
|
Umm, that ~sounds~ good - but what does it mean? In the 30+
years that I've been working with computer hardware, I've
never run across that expression for stopping the processor.
In situations were a runaway process could result in damage,
the normal method for halting a processor isn't via a status
semaphore, but by halting the CPU clock pulse stream -
either via grounding the output of the clock, or removing
power from the clock crystal. With no clock pulses, the CPU
cannot execute instructions, period. It's the only way to be
completely certain that the CPU will in fact stop.
Dale R.
| Quote: | ----------------------------------------
At 12:19 PM 9/16/2008 -0400, you wrote:
>
><simon(at)synchronousdesign.com>
>
>Jeff, although a good point to bring up, I highly doubt that such an
>important function would go to the microprocessor, except as a status
input.
>Surely it would go to a hard wired shut off circuit outside the micro
>to guarantee outside control without software being involved. If it
>didn't, it would be a major design error. However, all of these
>details are most likely proprietary data, and only Emagair would know.
>
>Simon
--------------------------------------
>Subject: Re: E-Mag P-Mag Safety info - Referenced
>msg from Mr. Cotner
>
>
>
>Any possibility that grounding the P-Lead would have no effect if the
>microcontroller was way too busy handling strangely timed interrupts
>due to the timing sensor bouncing around ? That would depend on
>whether the P-Lead is a standard input read by the microcontroller, or
>goes directly to some circuitry that shuts off the spark outputs.
>Anyone know how the circuirty is designed ?
>
>Jeff Page
>Dream Aircraft Tundra #10
|
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harley(at)AgelessWings.co
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| Posted: Fri Sep 19, 2008 4:27 am Post subject: Brad's reply on P-lead switch functionality |
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Dale Rogers wrote: | Quote: | --> AeroElectric-List message posted by: Dale Rogers <dale.r(at)cox.net> (dale.r(at)cox.net)
Robert L. Nuckolls, III wrote:
| Quote: | --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)cox.net> (nuckolls.bob(at)cox.net)
Received a reply from Brad on functionality of the p-lead switch
in Emag products:
"Grounding the p-lead 1) sends a status signal to the processor (telling it
to stop firing), and 2) disables the driver chips (so they can't fire)."
|
Umm, that ~sounds~ good - but what does it mean? In the 30+
years that I've been working with computer hardware, I've
never run across that expression for stopping the processor.
In situations were a runaway process could result in damage,
the normal method for halting a processor isn't via a status
semaphore, but by halting the CPU clock pulse stream -
either via grounding the output of the clock, or removing
power from the clock crystal. With no clock pulses, the CPU
cannot execute instructions, period. It's the only way to be
completely certain that the CPU will in fact stop.
Dale R.
|
Morning, Dale...
The way I read it, is that the P-lead "signal" tells the cpu to STOP FIRING (the spark plugs), not to stop. I assume that the processor continues running...the P-lead "signal" also disables the driver chips, which I assume are what actually direct the higher voltage to fire the spark plugs. These drivers are the devices that actually stop functioning.
So, the processor keeps running, but is told to stop firing the driver chips, and in case it doesn't, the driver chips are also disabled as a back up, I would assume.
Looking back on what I just wrote, a lot of assumptions, huh? <G>
Harley Dixon
[quote][b]
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dalamphere(at)comcast.net
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| Posted: Fri Sep 19, 2008 4:27 am Post subject: Brad's reply on P-lead switch functionality |
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Why would you intepret that statement to mean "stop the processor" ??
The way I read that statement "status signal sent to the processor (telling
it to stop firing)" meant the program that was running would no longer
execute the "ignition fire" routine.. It could be done with a simple "if"
statement, etc,... depends on the programming language used...
Made sense to me.
Dave L.
---
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simon(at)synchronousdesig
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| Posted: Fri Sep 19, 2008 11:07 am Post subject: Brad's reply on P-lead switch functionality |
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