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#1
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Damage using a serial cable to connect 2 PC's?
Hello again,
I have a basic question: is there any way I can damage either the serial port circuitry OR the MB itself by incorrectly (wrong pinouts, bad cable, link program doing something to the machine, etc.) when trying if a DB-9 serial cable with a null modem adapter will work? I am asking because my "USB on a 166MHz PI from 1997" experiment failed - there is no power going to the MB USB port connector pins - so I have given up. I am interested in trying a serial cable connection - Total Commander has it built in, and I also have several other DOS and Win programs for it. But I don't want to blow up either of the two computers. Is there any danger? Thanks. |
#2
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Damage using a serial cable to connect 2 PC's?
thanatoid wrote:
Hello again, I have a basic question: is there any way I can damage either the serial port circuitry OR the MB itself by incorrectly (wrong pinouts, bad cable, link program doing something to the machine, etc.) when trying if a DB-9 serial cable with a null modem adapter will work? I am asking because my "USB on a 166MHz PI from 1997" experiment failed - there is no power going to the MB USB port connector pins - so I have given up. I am interested in trying a serial cable connection - Total Commander has it built in, and I also have several other DOS and Win programs for it. But I don't want to blow up either of the two computers. Is there any danger? Thanks. http://en.wikipedia.org/wiki/RS-232 "Voltage levels RS-232 drivers and receivers must be able to withstand indefinite short circuit to ground or to any voltage level up to ±25 volts." That provides a good deal of protection against mistakes. Go for it. On the older RS232 driver chips, the biggest danger, was their lack of protection with respect to static discharge. Scuffing over the carpeting, then directly touching the pins, would be a bad idea. And if you somehow manage to burn that out, there is always the parallel port :-) Paul |
#3
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Damage using a serial cable to connect 2 PC's?
Paul wrote in
: http://en.wikipedia.org/wiki/RS-232 "Voltage levels RS-232 drivers and receivers must be able to withstand indefinite short circuit to ground or to any voltage level up to ±25 volts." That provides a good deal of protection against mistakes. That sounds pretty good. On the older RS232 driver chips, the biggest danger, was their lack of protection with respect to static discharge. Scuffing over the carpeting, then directly touching the pins, would be a bad idea. BION, I actually own *and* use an anti-static wrist strap. And I try not to get too static to begin with. Thanks for the reply. |
#4
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Damage using a serial cable to connect 2 PC's?
thanatoid wrote in
: Hello again, I have a basic question: is there any way I can damage either the serial port circuitry OR the MB itself by incorrectly (wrong pinouts, bad cable, link program doing something to the machine, etc.) when trying if a DB-9 serial cable with a null modem adapter will work? I am asking because my "USB on a 166MHz PI from 1997" experiment failed - there is no power going to the MB USB port connector pins - so I have given up. I am interested in trying a serial cable connection - Total Commander has it built in, and I also have several other DOS and Win programs for it. But I don't want to blow up either of the two computers. Is there any danger? Thanks. Some equipment uses 'TTL' levels (0=0.3V and 1=4.7V) but uses the same signal protocol. In most standard PC serial connections that's not standard, but watch out for it all the same. Interfacing the two standards is cheap, can be done with few parts, but damage can result otherwise, to the TTL side. Normally as Paul said, no problem. Serial is one of the most reliable metal-wired standards, which is why it refuses to die in heavy industry. In case you're not familiar... for binary file handling, try to get software that can handle Z-modem transfers. There are also X- and Y-modem standards, but Z-modem is by far the least awkward. I think it can also queue files so you don't have to nursemaid what can otherwise be a horribly tedious business. |
#5
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Damage using a serial cable to connect 2 PC's?
Lostgallifreyan wrote in
: Some equipment uses 'TTL' levels (0=0.3V and 1=4.7V) but uses the same signal protocol. In most standard PC serial connections that's not standard, but watch out for it all the same. Interfacing the two standards is cheap, can be done with few parts, but damage can result otherwise, to the TTL side. Normally as Paul said, no problem. Serial is one of the most reliable metal-wired standards, which is why it refuses to die in heavy industry. In case you're not familiar... for binary file handling, try to get software that can handle Z-modem transfers. There are also X- and Y-modem standards, but Z-modem is by far the least awkward. I think it can also queue files so you don't have to nursemaid what can otherwise be a horribly tedious business. Thanks, I appreciate the extra info. |
#6
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Damage using a serial cable to connect 2 PC's?
thanatoid wrote in
: Lostgallifreyan wrote in : Some equipment uses 'TTL' levels (0=0.3V and 1=4.7V) but uses the same signal protocol. In most standard PC serial connections that's not standard, but watch out for it all the same. Interfacing the two standards is cheap, can be done with few parts, but damage can result otherwise, to the TTL side. Normally as Paul said, no problem. Serial is one of the most reliable metal-wired standards, which is why it refuses to die in heavy industry. In case you're not familiar... for binary file handling, try to get software that can handle Z-modem transfers. There are also X- and Y-modem standards, but Z-modem is by far the least awkward. I think it can also queue files so you don't have to nursemaid what can otherwise be a horribly tedious business. Thanks, I appreciate the extra info. You're welcome. Anyone willing to respect a thing when it's good, not just denigrate it because it's 'old' is doing good things as far as I'm concerned. |
#7
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Damage using a serial cable to connect 2 PC's?
Lostgallifreyan wrote:
thanatoid wrote in : Hello again, I have a basic question: is there any way I can damage either the serial port circuitry OR the MB itself by incorrectly (wrong pinouts, bad cable, link program doing something to the machine, etc.) when trying if a DB-9 serial cable with a null modem adapter will work? I am asking because my "USB on a 166MHz PI from 1997" experiment failed - there is no power going to the MB USB port connector pins - so I have given up. I am interested in trying a serial cable connection - Total Commander has it built in, and I also have several other DOS and Win programs for it. But I don't want to blow up either of the two computers. Is there any danger? Thanks. Some equipment uses 'TTL' levels (0=0.3V and 1=4.7V) Just FYI, the logic levels are a bit off here. Actually, the TTL logic levels a Input: 0 to 0.8 V is a logic low input, and 2.2 to 5V is a logic high input. Output: 0 to 0.4 V for a logic low output, and 2.6 to 5V for a logic high output. |
#8
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Damage using a serial cable to connect 2 PC's?
"Bill in Co" wrote in
m: Lostgallifreyan wrote: thanatoid wrote in : Hello again, I have a basic question: is there any way I can damage either the serial port circuitry OR the MB itself by incorrectly (wrong pinouts, bad cable, link program doing something to the machine, etc.) when trying if a DB-9 serial cable with a null modem adapter will work? I am asking because my "USB on a 166MHz PI from 1997" experiment failed - there is no power going to the MB USB port connector pins - so I have given up. I am interested in trying a serial cable connection - Total Commander has it built in, and I also have several other DOS and Win programs for it. But I don't want to blow up either of the two computers. Is there any danger? Thanks. Some equipment uses 'TTL' levels (0=0.3V and 1=4.7V) Just FYI, the logic levels are a bit off here. Actually, the TTL logic levels a Input: 0 to 0.8 V is a logic low input, and 2.2 to 5V is a logic high input. Output: 0 to 0.4 V for a logic low output, and 2.6 to 5V for a logic high output. True. I was thinking of the 0.3V margin used for some digital IC's. Generally it's wise to use the stricter levels even for TTL if possible. It's meant to be forgiving (as is RS-232), but my main basis for the strict voltages is that 'TTL' is often used to describe levels for IC's that aren't nearly as forgiving. I think several systems made use of extra Schmitt trigger buffers to correct for this by forcing close approach to nominal voltage. Hopefully this isn't a problem anymore (as in such buffering is built in to most stuff). Anyway, sometimes it's easier to work to rule than to trust adherence to standards in something we can't control. Another point with the 0.3V margin is that it is often standardised as extending the other side of the nominal value, so safe limits at -0.3V and +5.3V respectively. I like it because it's easier to remember, and almost always guaranteed to work ok. I don't know how many parts are still prone to 'latch-up' when given signals before the device gets its own power, thus burning their own outputs when power arrives, but I read somewhere that staying inside this 0.3V limit is one of the easiest ways to reduce the risk (hence avoiding accidental mixes of TTL and RS-232 serial, even though some RS-232 is at 5V anyway, because that means also -5V exists). Last (but definitely NOT least) I have found that with some devices the baud rate has to be dropped very low to get good transfer even with cables no longer than 20 feet, suggesting that despite the robustness of the standards, some devices are not at all tolerant of weak voltage distinctions because they are much more vulnerable to noise. Every time, staying close to the nominal limit wins, so long as we stay inside, not outside, that limit. Afterthought: USB has encouraged a lot of people to forget completely that actual wires carry actual electrical energy, and to think purely of software. I have no idea how much of USB's quirks are due to driver errors, or electrical problems, but I suspect that very often a driver is unfairly copping the blame. I think that weak quality control might explain the erratic behaviour of the cheap USB widgets I have, more than any driver issues. |
#9
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Damage using a serial cable to connect 2 PC's?
In message , Bill in Co
writes: Lostgallifreyan wrote: [] Some equipment uses 'TTL' levels (0=0.3V and 1=4.7V) Just FYI, the logic levels are a bit off here. Actually, the TTL logic levels a Input: 0 to 0.8 V is a logic low input, and 2.2 to 5V is a logic high input. Output: 0 to 0.4 V for a logic low output, and 2.6 to 5V for a logic high output. There's even more to it: The levels Lg describes - 0 near 0V, and 1 similarly near +supply - are CMOS levels (and CMOS , at least 4000 series, doesn't have to run on 5V). TTL was/is based around a threshold (with margins) that is _not_ half-supply voltage, as you have correctly shown, but instead around 1.2V. But even within TTL, there are variations: whether it's the military (54xx) series or the commercial (74xx), let alone all the various families (plain, L, H, S, LS, ALS, AS, F, ...), though they're all supposed to be interoperable at least with a fanout of one. -- J. P. Gilliver. UMRA: 1960/1985 MB++G.5AL-IS-P--Ch++(p)Ar@T0H+Sh0!:`)DNAf In a time of drastic change it is the learners who inherit the future. The learned usually find themselves equipped to live in a world that no longer exists. -- Eric Hoffer (quoted by Elsie McGill , 1997-6-1). |
#10
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Damage using a serial cable to connect 2 PC's?
Absolutely no apologies for top posting.
Lostgallifreyan wrote :- Afterthought: - USB ... wires carry actual electrical energy (power), and .. I suspect that very often a driver is unfairly copping the blame. Especially when an unpowered USB hub is involved, perhaps using more than a couple of (even short) connecting cables. Always worth running usbview.exe as the first tool for troubleshooting USB issues. If you have a copy of the Win98 CD, then see the following URL and try the usbview.exe on the CD - "How to Use the Windows 98 USB Device Viewer Utility" http://support.microsoft.com/default...b;en-us;272584 or see http://www.ftdichip.com/Support/Utilities.htm for an alternative download (Microsoft USBView) Mart "Lostgallifreyan" wrote in message . .. "Bill in Co" wrote in m: Lostgallifreyan wrote: thanatoid wrote in : Hello again, I have a basic question: is there any way I can damage either the serial port circuitry OR the MB itself by incorrectly (wrong pinouts, bad cable, link program doing something to the machine, etc.) when trying if a DB-9 serial cable with a null modem adapter will work? I am asking because my "USB on a 166MHz PI from 1997" experiment failed - there is no power going to the MB USB port connector pins - so I have given up. I am interested in trying a serial cable connection - Total Commander has it built in, and I also have several other DOS and Win programs for it. But I don't want to blow up either of the two computers. Is there any danger? Thanks. Some equipment uses 'TTL' levels (0=0.3V and 1=4.7V) Just FYI, the logic levels are a bit off here. Actually, the TTL logic levels a Input: 0 to 0.8 V is a logic low input, and 2.2 to 5V is a logic high input. Output: 0 to 0.4 V for a logic low output, and 2.6 to 5V for a logic high output. True. I was thinking of the 0.3V margin used for some digital IC's. Generally it's wise to use the stricter levels even for TTL if possible. It's meant to be forgiving (as is RS-232), but my main basis for the strict voltages is that 'TTL' is often used to describe levels for IC's that aren't nearly as forgiving. I think several systems made use of extra Schmitt trigger buffers to correct for this by forcing close approach to nominal voltage. Hopefully this isn't a problem anymore (as in such buffering is built in to most stuff). Anyway, sometimes it's easier to work to rule than to trust adherence to standards in something we can't control. Another point with the 0.3V margin is that it is often standardised as extending the other side of the nominal value, so safe limits at -0.3V and +5.3V respectively. I like it because it's easier to remember, and almost always guaranteed to work ok. I don't know how many parts are still prone to 'latch-up' when given signals before the device gets its own power, thus burning their own outputs when power arrives, but I read somewhere that staying inside this 0.3V limit is one of the easiest ways to reduce the risk (hence avoiding accidental mixes of TTL and RS-232 serial, even though some RS-232 is at 5V anyway, because that means also -5V exists). Last (but definitely NOT least) I have found that with some devices the baud rate has to be dropped very low to get good transfer even with cables no longer than 20 feet, suggesting that despite the robustness of the standards, some devices are not at all tolerant of weak voltage distinctions because they are much more vulnerable to noise. Every time, staying close to the nominal limit wins, so long as we stay inside, not outside, that limit. Afterthought: USB has encouraged a lot of people to forget completely that actual wires carry actual electrical energy, and to think purely of software. I have no idea how much of USB's quirks are due to driver errors, or electrical problems, but I suspect that very often a driver is unfairly copping the blame. I think that weak quality control might explain the erratic behaviour of the cheap USB widgets I have, more than any driver issues. |
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