In the 70's I worked on such a design, and used an 8048 emulator to debug the device. We originally used Intel 8255's, but got some National's in and when I brought the power up on the device before starting the MCU, all the outputs in the Nat. part latched on and the print solenoids, which were designed only for _momentary_ energization, were driven continuously. Before I could remove power, the print solenoids fried. The Intel part did not do this. I had to replace the solenoids from another damaged printer to get the thing running. (deadlines....) Mark ----- Original Message ----- From: "Harold M Hallikainen" To: Sent: Friday, June 08, 2001 11:32 AM Subject: Re: [OT]: OEM Printer Suggestion > This reminds me of something to consider during initialization. Since > I/O ports are in input mode on reset, lines that are driving your > printhead drivers are floating. You COULD get all printhead drivers on > simultaneously during the time prior to setting the TRIS registers. > Appropriate pull-up or pull-down resistors in front of the drivers can > solve this. > I once had an impact dot matrix printer that would fairly often blow > fuses on power up. All the print wire solenoids were hit simultaneously > until the processor finished initialization. > > Harold > > > On Fri, 8 Jun 2001 10:58:39 -0500 David VanHorn > writes: > > At 11:33 AM 6/8/01 -0400, Shawn Yates wrote: > > >Oh, that makes it sound much more interesting!! > > > > The one I went through, needed a power supply that could deliver > > pulses of > > 19A @ 32V to print a full black line. The pulse was something like > > 300uS > > wide. Definitely takes some good PCB routing too. > > > > -- > > Dave's Engineering Page: http://www.dvanhorn.org > > > > I would have a link to > > http://www.findu.com/cgi-bin/find.cgi?KC6ETE-9 here > > in my signature line, but due to the inability of sysadmins at > > TELOCITY to > > differentiate a signature line from the text of an email, I am > > forbidden to > > have it. > > > > -- > > http://www.piclist.com hint: The PICList is archived three different > > ways. See http://www.piclist.com/#archives for details. > > > > > > FCC Rules Online at http://hallikainen.com/FccRules > Lighting control for theatre and television at http://www.dovesystems.com > > ________________________________________________________________ > GET INTERNET ACCESS FROM JUNO! > Juno offers FREE or PREMIUM Internet access for less! > Join Juno today! For your FREE software, visit: > http://dl.www.juno.com/get/tagj. > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.