Simple Clockable Decoder Chip
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From: Tomás Ó hÉilidhe on 6 May 2008 18:11 On May 6, 9:35 pm, Hans-Bernhard Bröker <HBBroe...(a)t-online.de> wrote: > > People advised me about this. They said stuff like "if a bit of noise > > gets onto...". The way I see it though, if I can't rely on electronics > > then there's no point in me even trying to get things to work. > > That's rich, coming from you. Not really, in fact I think it's to be expected considering I'm a novice at this stuff and I'm explicitly asking people's advice here on what to do. > You could rely on electronics alright. You would have to stop > *designing* them with such total, aggressive disregard to reliability, > though. Hypothetically speaking, if I couldn't rely on a counter incrementing from 011 to 100, then why should I bother even trying to use it in a design? This is what I'm trying to understand. > It's become clear that you don't listen to any advice along > those lines. That's your decision to make, sure, but that also makes > all advers consequences entirely your fault. We did tell you so. Well I'd hardly post entire threads here looking for advice if I was going to disregard the responses. > > I've left my current board on overnight for three nights in a row and > > it was still synchronised. > > How do you know it's "still" synchronized, as opposed to having rebooted > and re-synchronized itself 20 times (always while you weren't looking) over? If the microcontroller were to reboot, then the LED matrix would be in a totally different state. Alas, when after the three nights, the display is exactly the way I left it. > Anyway, a test like that proves diddly-squat. You have to stress it to > expose flaws. Switch on a mobile phone directly on top of your device. > Fire up a piezo lighter in different places. Heat it. Cool it. Drop > it. Flex it. In short: let it see some abuse. So are you advocating using two pins to control the shift register, rather than one?
From: Tomás Ó hÉilidhe on 6 May 2008 08:06 On May 6, 8:10 am, Eric Smith <e...(a)brouhaha.com> wrote: > Tomás Ó hÉilidhe wrote: > > As I said elsethread, I've decided to run a 4-Bit counter into a 4- > > to-16 decoder. > > That will work fine, as long as you don't mind the decoding glitches. Decoding glitches? Please explain.
From: rickman on 6 May 2008 09:24 On May 5, 5:12 pm, Tomás Ó hÉilidhe <t...(a)lavabit.com> wrote: > On May 5, 9:33 pm, Eric Smith <e...(a)brouhaha.com> wrote: > > > Tomás Ó hÉilidhe <t...(a)lavabit.com> writes: > > > > The only problem though is that I need a chip that will count to 16 > > > instead of 10. Does anyone know of a similar chip that will cycle thru > > > 16 different outputs? > > > Sure, a CPLD. Xilinx XC9536 (5V) or XC9536XL (3.3V) come to mind. > > Too expensive. > > As I said elsethread, I've decided to run a 4-Bit counter into a 4- > to-16 decoder. What is your cost limit? CPLDs are pretty cheap. I want to say I have seen devices for around a dollar US. Even obsolete logic chips aren't much cheaper than that. Is this intended to teach you something? If so, I would *require* you to use a CPLD if I were the instructor. There is very little value in learning to use chips that were designed long before the PC. Does your instructor also ask you to use a dial phone? Do you connect to your computer using a TTY? (do you know what a TTY is?) Rick
From: linnix on 6 May 2008 11:01 On May 6, 6:24 am, rickman <gnu...(a)gmail.com> wrote: > On May 5, 5:12 pm, Tomás Ó hÉilidhe <t...(a)lavabit.com> wrote: > > > On May 5, 9:33 pm, Eric Smith <e...(a)brouhaha.com> wrote: > > > > Tomás Ó hÉilidhe <t...(a)lavabit.com> writes: > > > > > The only problem though is that I need a chip that will count to 16 > > > > instead of 10. Does anyone know of a similar chip that will cycle thru > > > > 16 different outputs? > > > > Sure, a CPLD. Xilinx XC9536 (5V) or XC9536XL (3.3V) come to mind. > > > Too expensive. $1.07 qty 1 at digikey: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=122-1385-ND > > > As I said elsethread, I've decided to run a 4-Bit counter into a 4- > > to-16 decoder. > > What is your cost limit? CPLDs are pretty cheap. I want to say I > have seen devices for around a dollar US. Even obsolete logic chips > aren't much cheaper than that. Only if you can find them. > > Is this intended to teach you something? The idea is to teach him what not to do in real life. In real apps, we would not be constrainted to a 20 pins PIC. All his logics can be replaced with a 44 pins uC for 50 cents. > If so, I would *require* you > to use a CPLD if I were the instructor. There is very little value in > learning to use chips that were designed long before the PC. Does > your instructor also ask you to use a dial phone? Do you connect to > your computer using a TTY? (do you know what a TTY is?) > > Rick
From: cs_posting on 6 May 2008 11:03
On May 5, 5:12 pm, Tomás Ó hÉilidhe <t...(a)lavabit.com> wrote: > As I said elsethread, I've decided to run a 4-Bit counter into a 4- > to-16 decoder. In what way is that superior to daisy chaining two shift-register type devices? The only justification I see is if you either also have a use for the binary coded count, or you have those two parts in your junk box and don't have a pair of the others, or something similarly out-of-band (like a different logic family that doesn't include that function, whatever) |