Subject: Re: Urgent help needed to blank monitor
Date: Wed, 06 Nov 2002 02:33:53 -0800
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"N. Coesel" wrote:
> "Ulrich Peters" wrote in message
> > Hello again.
> > I think it might be best to expect a certain bit pattern on the parallel
> > port, to get one logical high (or low) to control the circuit, because
> > the serial port is already in use by a bill acceptor, and the sound card
> > is used to provide acustical feedback to the user during the normal
> > operation of the software.
> > Although a 555 timer could be used to create a delay to switch on the
> > monitor, I prefer to use the parallel port solution, because I would
> > have control over the shutdown process as well. The equipment has a
> > button on its back to power down the equipment. Before my software shuts
> > down, the last thing it could do is quickly send a new byte to the
> > parallel port, turning off the monitor, before Windows shows its usual
> > shutdown dialogs ("saving settings", "closing connections", etc.).
> > Unless you send new data to the parallel port, the last byte sent
> > "sticks".
> I wouldn't rely on that. I've made an eprom emulator connected to a parallel
> port. Bit banging seemed not to work because the last byte didn't always
> 'stick' (I didn't lock the printerport). For this reason I made my eprom
> emulator mimic a printer port. This is fairly easy. If you have a latch
> (like a 74HCT573 or a 74HCT574) and clock it from the strobe line, you can
> simply send printer output to your circuit. If you take 2 comparators (like
> 74HCT688) you can select an on-character and an off-character. The
> comparators's outputs should be connected to a flipflop with (pre)set and
> clear inputs (like 74HCT74).
> Reply to: nico nctdev nl @ .
Some operating systems read the startup screen from a file. Can you
make the startup splash screen a blank??
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