14 Aug
2010
14 Aug
'10
7:20 p.m.
Dave McGuire <mcguire at neurotica.com> wrote:
Apparently so. :-)
Yup. I just learned. All I've ever seen have been with detachable cords.
But as I wrote above, I bet this is a european thing.
All mine do, and I have four right here.
Huh? That is totally backwards in more than one way.
Yes, MMJ "fixed" one thing. It has nothing to do with ethernet, but all
to do with people (and companies) who couldn't figure out how to wire a
DB25. Almost all companies got the gender wrong on their equipment. In
addition to that, many couldn't figure out what a DTE and DCE was.
Now, that is called standard violation. Causing people to have cables
they think they can connect, but which don't work. DEC is one of the two
companies that did get it right (the other one being HP). To this day,
it totally amaze me how so many companies couldn't get this right. And
I don't know. When was the end of the monochrome CRT era? Has it ended yet?
Dave McGuire <mcguire at neurotica.com> wrote:
Ouch. You're right. For some reason I was thinking that the VT220 also
had MMJ, but it didn't. That only came with the VT320...
But I can't see the relevance of MMJ vs. RJ45 either, for various
reasons mentioned above.
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt at softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
On 8/13/10 4:27 AM, Johnny Billquist wrote:
Hmm. Unfortunately I don't have any VT320 around anymore, since all of
them have broken down (flybacks mostly). But I've had atleast five of
them over time, and all have had removable cords.
I wonder if this might be more of a european thing. Since different
countries in Europe use different power plugs, it makes sense to have
the power cord detachable. There is more or less a standard format plug
that goes into any kind of computer equipment, but the wall plug differs
between countries. So you usually don't use a fixed power cord, but
instead the standard equipment power connector on your equipment, and
then ship whatever power cord is used in that country.
> >> Not at all, I just wanted to know
what he didn't like about them. The
> >> only thing I dislike about VT420s is the non-removable power cables.
>
> Huh? My VT420s have removable power cords...
Mine do not. This is interesting. I know there was a variation of
the VT320 (yes 320) that had a removable power cord, but they're not
terribly common. Apparently there's a removable-cord version of the
VT420 as well. Interesting! > The VT420
have both DB25 and MMJ, so I can't see how that could annoy
> anyone. (As do all DEC terminals from the VT220 onwards.)
Now waitaminute. I am staring at the back of both a VT420 and VT320
right now, on the table opposite my desk. Neither of them have DB25s,
only MMJs. The VT420 has what looks like a knock-out that's about the
right size for a DB25.
Apparently versions with and without DB25s exist as well! That same (rare-to-me) VT320 I mentioned above that
has a removable
power cord also has a DB25. Out of a few hundred VT320s that have gone
through my hands, it's the only one I've ever seen that has either a
removable power cord or a DB25. I've never seen a VT420 with either of
those, and until now, I haven't even heard of their existence.
Well, I have four VT420 at home right now, and they all have both a DB25
and detachable power cord. Since I was feeling creative tonight, I even
took pictures of the back side of all terminals I have at home.
So here is a link to where you can see the backside of:
VT-330, VT-420, VT-510, VT-520 and VT-525. All of them have DB25 and all
of them have detachable power cords.
http://www.update.uu.se/~bqt/vt
(Argh, I just realized I missed the VT-240 I have, but oh well...)
William Donzelli <wdonzelli at gmail.com> wrote:
> Huh? My
VT420s have removable power cords...
Some do, some do not. > The VT420
have both DB25 and MMJ,
Some do, some do not. Of the fifty or so I had recently, I think only
one had the DB25 in addition to MMJ. > However,
MMJ is actually very nice. Too bad it didn't catch on outside of
> DEC. But I try to use it for everything I can at home.
MMJ "fixed" a problem that really was no big deal - people confusing
RJ45 serial with ethernet. I think the real reason was to lock people
into MMJ by doing the old lets-violate-the-standard trick. In my book,
DEC is guilty as anyone else here. from that perspective it don't surprise me when
people around here don't
get it either (there was a long thread not long ago,
which I declined to
even participate in). RS-232 is so simple that it's hard to get wrong.
There is only two things you can mess up with. Connector gender, and DTE
vs DCE. How can people find that so difficult???
And if people and companies had actually stayed with the standard, you
wouldn't even had been able to mix those to parameters up.
A DTE *should* have a *male* DB25. A DCE *should* have a female DB25. A
male-male cable should be crossed, a female-female cable should be
crossed, a male-female cable should be straight. There is nothing more
to it.
All terminals and computers are DTEs. Modems are DCEs. But it you
absolutely wanted to, feel free to wire a modem up as a DTE. It will
work just fine, just as long as you fit the right DB25 to it, and wire
it up accordingly.
But no. Companies just loved putting female DB25 on their terminals, and
wire them up as DTEs. Or put male DB25 on their computers, and wire them
up as DCEs. *Idiots*
That is called violating the standards.
And to make matters ridiculously worse, we have IBM. Who simply put just
raped the RS-232 standard by using a DE9, moving one or two pins in a
totally non-logical way, changing the gender, *and* sortof wiring it as
a DCE.
They should be taken out to the back and shot. IBM have caused more
damage to the computer world than all other companies put together.
Here is a simple tip for the next time you wire a RS-232 up. Measure pin
2 and 3 on the equipment. One should at around -12V, while the other is
around 0. Do this on both sides. Then wire the -12V from one side to the
0V on the other for both 2 and 3. And run pin 7 straight through.
And that's it. You now have a correct RS-232 cable, albeit just the data
leads. You can wire the rest up if it amuse you. The most important ones
are DCD, DTR, DSR, RTS, CTS. For a DTE-DTE, you should wire CTS to RTS
and DCD+DSR to DTR. Very simple. And if I remember right, we're talking
about pines 4,5,6,8 and 20. But I'd usually check the RS-232 DB25
connector layout before I try to wire a full cable up. Most of the time
I'm happy with just 2,3 and 7 anyway, since I don't do hardware flow
control (another RS-232 standards violation, by the way, and which DEC
did not do). But having the DSR signal is useful to detect if someone
gets disconnected.
What DEC did with MMJ was in no way violating any standard. Noone in his
right mind would think that an MMJ was an RS-232. So what standard did
they violate (if I may ask?). Hmm, I seem to remember that the
signalling in the MMJ is even called DEC-423, but I might be remembering
wrong. It is pretty much compatible with RS-423 anyway (might be
equivalent), and you can usually get away with connecting that directly
with RS-232, but they are not really the same thing. (Hmm, looking at
RS-423, it would appear that DEC-423 is a superset, since DEC-423 don't
actually use a common ground for everything, but use one ground for all
transmitted signals, and one ground for all received signals).
So, the signalling in the MMJ connector is only claimed to be
communicating using DEC-423. How would that violate any standard? If DEC
had said that it was an RS-232 port, then they would have violated the
RS-232 standard. (I guess I'm confused at your definition of violating a
standard.)
What MMJ solved was that they removed the gender issues, and they
simplified the DTE/DCE issues. Your cable is either straight or crossed
(either flat or turned 180? looking from one end to the other). They
also simplified the assembly of the cables compared to RS-232. The fact
that MMJ
Ethernet vs. RS-232 on a RJ45? Give me a break. None of that even
existed when the MMJ came about. And the idea of putting RS-252 on an
RJ45 is something I'd call violating a standard, if anything. But it
comes with the one-connector-for-everything that some people are so fond
of. So you also have telephony on RJ45, to make life really
interesting... And all running through one patch panel.
> The
reliability of the VT420 seems to be pretty decent. I've had many more
> VT320 fail on me. But we have to remember that we're talking about 20+ year
> old equipment now...
Yes, but these were built well towards the end of the monochrome CRT era. On 8/13/10 5:51 PM, Johnny Billquist wrote:
I said "unless you count the used defined font". :-)
All that said, I know some crazy person wrote a GIF viewer for the
VT320, using the user defined font to pull it off.
Dave McGuire <mcguire at neurotica.com> wrote:
On 8/13/10 8:49 PM, William Donzelli wrote:
> >> AFAIK the VT420 supports Sixel,
but not ReGIS.
>
> No. The last graphic terminal was the VT340.
> The VT420 don't support any graphics, unless you count the user defined
> font as graphics.
>
> Graphics implies either SIXEL, ReGIS or both. Actually, I've never seen
> any terminal that supports sixel but not ReGIS, however, several
> printers is of that inclination.
>
> (Although I'm sure someone will now recall some terminal that do sixel
> but not ReGIS just because I wrote the above... :-) ).
I've never *used* Sixel graphics on a VT420, but the manual clearly
states that it supports the Sixel format.
(flip flip)
Ok, I just went back and re-read it. It "supports Sixel format" as a
way to encode user-definable character sets. So you're right I suppose,
it ALMOST supports Sixel graphics! ;) > >>
However, MMJ is actually very nice. Too bad it didn't catch on outside of
> >> DEC. But I try to use it for everything I can at home.
>
> MMJ "fixed" a problem that really was no big deal - people confusing
> RJ45 serial with ethernet.
Huh? I don't see how that can be. The 802.3i standard which defined
10baseT Ethernet on RJ45 connectors came out in 1990, while the first
terminal to implement MMJ was the VT320, which predates that by three years. 
14 Aug
14 Aug
8:14 p.m.
Almost all companies got the gender wrong on their
equipment.
For "almost all companies" to get the gender wrong, somehow we
managed. Mostly, it was just making or ordering cable Y instead of
cable X.
And to make matters ridiculously worse, we have IBM.
Who simply put just
raped the RS-232 standard by using a DE9, moving one or two pins in a
totally non-logical way, changing the gender, *and* sortof wiring it as a
DCE.
DG also used non standard DEs I think. Moving serial to the DE was in
the cards, simply because the DB was underutilized and took up too
much real estate.
IBM certainly played the standard violation game as well, but somehow
the DE9 serial issue is no big deal. Order or make cable Z, and the
problem is solved.
What DEC did with MMJ was in no way violating any
standard.
right mind would think that an MMJ was an RS-232. So what standard did they
violate (if I may ask?).
A new connector that requires new tooling. Every halfway decently
sized DP shop probably had a nice selection of tools and supplies for
D shell and RJ connectors. Male or female - no problem to make
whatever. Or call up the cable supplier or Inmac, and let do the work.
But not with MMJ, everyone has to get that special die...
Ethernet vs. RS-232 on a RJ45? Give me a break. None
of that even existed
when the MMJ came about.
OK, yes, I suppose it is a bit early, so I will take that back (but,
come on, lighten up a bit. Did I touch a nerve?). I was told that
DEC's reason is that too many people were confusing things that use RJ
connectors. However, it was pretty clear at the time that RJs were
going to be a hit. Serial went there, and even token ring.
I don't know. When was the end of the monochrome
CRT era? Has it ended yet?
Yes, it has ended. Monochome CRTs have not been made for quite a few
years now. "New" production terminals are using refurbished tubes.
Also, I bet the number of new dumb terminals being ordered these days
is tiny, and it would not surprise me if what is being sold today as
new is just old stock from the warehouses. I is a whole lot cheaper to
store a few thousand terminals in a warehouse than it is to keep a
very slow production line open, with the bonus that unsold stock can
be written off and scrapped.
--
Will
9:26 p.m.
On 8/14/10 8:14 PM, William Donzelli wrote:
IBM certainly played the standard violation game as
well, but somehow
the DE9 serial issue is no big deal. Order or make cable Z, and the
problem is solved.
DE-9 serial ports!! *spit*
OK, yes, I suppose it is a bit early, so I will take
that back (but,
come on, lighten up a bit. Did I touch a nerve?). I was told that
DEC's reason is that too many people were confusing things that use RJ
connectors. However, it was pretty clear at the time that RJs were
going to be a hit. Serial went there, and even token ring.
Modular connectors date back to early 1973. They were adopted in the
telephony world pretty quickly, but there wasn't that much of an overlap
between that world and the world of computing. (nowhere near as much as
in later years, I mean)
AT&T StarLAN predates 10baseT Ethernet, and I seem to recall it using
modular connectors as well, but I don't know when it came into being. I
only started seeing mention of it in the mid-1980s. Perhaps that
could've been a source of the confusion DEC was trying to address with MMJ.
That said, though, while the sequence of events largely precludes that
motivation stemming from confusion involving 10baseT in particular, it
was a good thing to do. Perhaps they should've done it in a different
way, using a different standard connector if they really didn't want
DB-25s (which they SHOULD have used), but look at all the trouble we're
still having on TODAY between 10/100/1000baseT Ethernet and serial ports
on networking equipment, and even other types of connections. Just a
few months ago I unplugged a T1 (RJ48X, the same connector as an RJ45)
from the serial CONSOLE port on a Cisco and plugged it
back into its T1
WIC card. The "tech" had gotten them mixed up.
So yes, all over the industry we have connector confusion problems
primarily because people refuse to pay attention to what they're doing.
I'd dearly love to see 120V AC power delivered on 1/8" headphone jacks
for a few years...just to clean up the gene pool a bit.
Yes, it has ended. Monochome CRTs have not been made
for quite a few
years now. "New" production terminals are using refurbished tubes.
Also, I bet the number of new dumb terminals being ordered these days
is tiny, and it would not surprise me if what is being sold today as
new is just old stock from the warehouses. I is a whole lot cheaper to
store a few thousand terminals in a warehouse than it is to keep a
very slow production line open, with the bonus that unsold stock can
be written off and scrapped.
I have a mono VGA CRT here that was purchased new less than a year
ago. I suppose its CRT could've been a refurb.
-Dave
--
Dave McGuire
Port Charlotte, FL
14 Aug
14 Aug
10:54 p.m.
New subject: Useful cables (was Re: Terminals...)
At 9:26 pm -0400 2010/08/14, Dave McGuire wrote:
I'd dearly love to see 120V AC power delivered on
1/8" headphone jacks
for a few years...just to clean up the gene pool a bit.
The necessary adapters exist, and are readily available from any photo shop
that carries pro lighting gear.
Examples:
http://www.bhphotovideo.com/c/product/682580-REG/Impact_10032330_Sync_Cord_…
http://www.bhphotovideo.com/c/product/613977-REG/Impact_9031510_Mini_3_5_mm…
--
Kevin Schoedel <schoedel at kw.igs.net> VA3TCS
15 Aug
15 Aug
4:23 a.m.
New subject: Useful cables (was Re: Terminals...)
On 8/14/10 10:54 PM, Kevin Schoedel wrote:
We need to see to it that a very large number of these find their way
out into the general public. =)
-Dave
--
Dave McGuire
Port Charlotte, FL
I'd dearly
love to see 120V AC power delivered on 1/8" headphone jacks
for a few years...just to clean up the gene pool a bit.
The necessary adapters exist, and are readily available from any photo shop
that carries pro lighting gear.
Examples:
http://www.bhphotovideo.com/c/product/682580-REG/Impact_10032330_Sync_Cord_…
http://www.bhphotovideo.com/c/product/613977-REG/Impact_9031510_Mini_3_5_mm…
2:33 p.m.
On 8/14/10 8:14 PM, William Donzelli wrote:
If EE-9s were the only non-standard serial ports I had to deal with, I
would be happy. But I've got them on DB25s, DE9s, DC37s (!) (4 poirtson
one connector..), 5 pin quincuncial DIN plugs, 8 pin DIN plugs, 8 pin
mini-DINs (and no, not the Mac version), 3-contact jack plugs, 4 pin 2mm
headers, 10 pin 2mm headers (2 different versions), 50 pin microribbons,
36 pin microribbons, various PCB card edge conenctors etc, etc, etc. But
actually, I've had many worse thigns to sort out. Mostly it's justr a
matter of matching up signals...
IBM certainly played the standard violation game
as well, but somehow
the DE9 serial issue is no big deal. Order or make cable Z, and the
problem is solved.
DE-9 serial ports!! *spit* So yes, all over the industry we have connector
confusion problems
primarily because people refuse to pay attention to what they're doing.
I'd dearly love to see 120V AC power delivered on 1/8" headphone jack
for a few years...just to clean up the gene pool a bit.
The first problem is that jack plugs (as we call them) tend to
monetarily short when plugged in or pulled out...
I have no idea what the flashover voltage of such a connector is, but I
am likely to measure it jsut to see...
-tony
14 Aug
14 Aug
9:48 p.m.
In article <4C6724B7.3090908 at softjar.se>,
Johnny Billquist <bqt at softjar.se> writes:
Almost all companies got the gender wrong on their
equipment.
That is telling you something about the standard. If
everyone's getting it wrong, then the standard has a bug.
Standards should make it easy for people to do the right thing.
If a standard comes out and everyone consistently gets it wrong, then
the standard is at fault, not the people.
Standards should acknowledge human nature, not pretend that humans are
vulcans.
[...] many couldn't figure out what a DTE and DCE
was.
More testimony to the standard being buggy.
It doesn't help that these two different roles differ in their acronym
by only a single letter that sounds almost identical when pronounced
out.
--
"The Direct3D Graphics Pipeline" -- DirectX 9 draft available for download
<http://legalizeadulthood.wordpress.com/the-direct3d-graphics-pipeline/>
Legalize Adulthood! <http://legalizeadulthood.wordpress.com>
15 Aug
15 Aug
2:37 p.m.
It doesn't help that these two different roles
differ in their acronym
by only a single letter that sounds almost identical when pronounced
out.
'Charlie' doesn't sound a bit like 'Tango' to my ears...
Going very off-topic., the one I find worry is that (in the UK, at
least), medical doctors use 'hypo-' to mean 'too low' and 'hyper-'
to
mean 'too high'. Those do sound very similar, and the consequences of
getting it wrong are a lot worse than having to re-wire a DB25...
-tony
2:23 p.m.
>>
>> Not at all, I just wanted to know what he didn't like about them=
.
The
>> >> only thing I dislike about
VT420s is the non-removable power cable=
s.
>=20
> Huh? My VT420s have removable power cords...
=20
Mine do not. This is interesting. I know there was a variation of
the VT320 (yes 320) that had a removable power cord, but they're not
terribly common. Apparently there's a removable-cord version of the
VT420 as well. Interesting! Huh? That is totally backwards in more than one way.
Yes, MMJ "fixed" one thing. It has nothing to do with ethernet, but all=20
to do with people (and companies) who couldn't figure out how to wire a=20
DB25. Almost all companies got the gender wrong on their equipment. In=20
addition to that, many couldn't figure out what a DTE and DCE was.
Now, that is called standard violation. Causing people to have cables=20
they think they can connect, but which don't work. DEC is one of the two=20
companies that did get it right (the other one being HP). To this day,=20
This must be a totally different HP to the one I've come across...
If HP used a male connector on a piece of equipment, it was DTE. But if
they used a female conenctor, it might be DTE, it might be DCE. I've lost
count of the number of HP printer ports (both on computers/terminals and
on printers) which are DTEs on a female connector.
Mnay HP devices had a 50 pin microribbon connector for the serial port.
It was actually quite nice, in that it might carry RS422 signals as well
as RS232, and it would have the +/-12V ans +5V poiwer lines avaialble for
interface converters. HP sold cables to link it to normal DB25s (and I
think they sold 'standard violating cables' such as a male DB25 wired as
a DCE!)
And then there's the HP82164... It has a male connecotr, but an internal
jumper block that can switch it between DTE and DCE wiring (!). And i
nthe DCE mode, some of the connections are _weird_. I find the onyl sane
way to use that device is to keep that jumper set to DTE and make up the
cables as necessary.
Heck, I've even got an HP RS232 interface unit with a cable ending ina 36
pin microribbon plug, like a Centronics printer conenctor. Origianlly it
would ahve come with an adapter from that to DB25s, but of course that
can get lost...
So I do not regard H Pas one of the 'good guys' here...
it totally amaze me how so many companies couldn't
get this right. And=20
from that perspective it don't surprise me when people around here don't=20
get it either (there was a long thread not long ago, which I declined to=20
even participate in). RS-232 is so simple that it's hard to get wrong.=20
There is only two things you can mess up with. Connector gender, and DTE=20
vs DCE. How can people find that so difficult???
My view is that DTE/DCE is different from either conenctor gender or
wiring. The reason is that RS232 is not quire symmetrical. Sure, there
are obvious pairs of signals that everybody knows swap with each ohter --
TxD <-> RxD, RTS <-> CTS, DSR <-> DTR. But there are also many signals
that don't have a couterpart going the other way. The most common one is
DCD (carrier detect) which is DCE->DTE only. And the second most common
one is RI (Ring indicator). There are many more, though (DRS -- DAta Rate
Select is from DTE to DCE, for xample).
Given that, my view is that a device where DCD is an input is a DTE no
moatter what connector is used, what gender of connector is used, and how
it's wired.
This implies that I consider the HP 50 pin interface to be a DTE, BTW.
And if people and companies had actually stayed with
the standard, you=20
wouldn't even had been able to mix those to parameters up.
True enough.
A DTE *should* have a *male* DB25. A DCE *should* have a female DB25. A=20
male-male cable should be crossed, a female-female cable should be=20
Perhaps you could give explicint wirelists for a 'crossed' cable that
always works. Because I sure can't!
crossed, a male-female cable should be straight. There
is nothing more=20
to it.
I disagree there...
All terminals and computers are DTEs. Modems are DCEs. But it you=20
I have seen computers with DCE ports. Really DCE -- that is a female
connector, wired as a DCE. The idea is you can plug a terminal straight in.
absolutely wanted to, feel free to wire a modem up as
a DTE. It will=20
I don;t think you can. What are you going to do with DCD and RI? They are
outputs from amodem, what pins on a DTE connector are you going to
connect htem to.
And to make matters ridiculously worse, we have IBM.
Who simply put just=20
The original PC Asyunc card (and IIRC at least one of the synchronous
cards) got it right. A DB25 male, wired as a DTE. That seems to fit the
standard.
raped the RS-232 standard by using a DE9, moving one
or two pins in a=20
totally non-logical way, changing the gender, *and* sortof wiring it as=20
a DCE.
Err, no. It's a DTE (clearly, since the DCD and RIO pins are inputs, and
in fact the pin named TxD is an output, etc). It's a male connector (as a
DTE should be). All they did was use a DE9 connector and define a pinout
for it. I don't think that's a big problem. BTW, the standard IBM cable
for this (as docuemtned in the manuals) has a DE9 socket to fit the card
linked ot a DB25 plug, and that is wired as a DTE. Which IMHO meets the
standard.
They should be taken out to the back and shot. IBM
have caused more=20
damage to the computer world than all other companies put together.
While I have no particular love of IBM, I don;t think this is a fair
comment at all. And I certainyl don't think their version of the RS232
interface violtates anything much.
Here is a simple tip for the next time you wire a RS-232 up. Measure pin=20
2 and 3 on the equipment. One should at around -12V, while the other is=20
around 0. Do this on both sides. Then wire the -12V from one side to the=20
0V on the other for both 2 and 3. And run pin 7 straight through.
I find those little adapters with 7 or so bicoloured LEDs useful for
this. Pity they are hard to get now...
I assume fro mthe pin numbers you are using DB25 connectors. In which
case you shouldalwo wire pin 1 straight through using the screen
(shield) of the cable. If you're going to complain about violating
sandards....
And that's it. You now have a correct RS-232
cable, albeit just the data=20
leads. You can wire the rest up if it amuse you. The most important ones=20
Problem is, a lot of devices require at least some of those control
signals to be asserted... And some devices use odd ones (pin 11 as a busy
signal is a favourite of many printers!). If you don't wire them
correctly, eitherr you lose data when the buffer fills, or nothing works
at all.
I have 3 things which make life a lot easier. The first one violates the
standards, but it helps to undo violations...
1) A 'all gender cahle'This is a lenght of 25 way IDC cable with a DB25
plug and a DB5 socket at both ends (4 connectors total). Used when some
idiot has wired a DTE on a socket, for example.
2) A 'loopbakc handshake' null modem adapter. This wires 7 striaght
through, swapps 2 and 3, and straps 4 to 5 and 6 to 8 to 20 at each end.
3) A 'full handshake' null modem adapter. 7 staight through, swap 2 with
3, 4 with 5 and 6 and 8 (strapped) with 20.
Some devices need moe trickery, which is why I have a breakout box. And
various special cables and adapters kept with the devices in question.
are DCD, DTR, DSR, RTS, CTS. For a DTE-DTE, you should
wire CTS to RTS=20
and DCD+DSR to DTR. Very simple. And if I remember right, we're talking=20
about pines 4,5,6,8 and 20. But I'd usually check the RS-232 DB25=20
Yes.
connector layout before I try to wire a full cable up.
Most of the time=20
The common pins for the DB25 wiring iare burnt into my brain. But I have
to look up things like the back channel connections (yes, I do have at
least one device that implements that).
I'm happy with just 2,3 and 7 anyway, since I
don't do hardware flow=20
control (another RS-232 standards violation, by the way, and which DEC=20
Indeed it is. Originally modems didn't buffer data. The control lines
were between the modem and the termnial/computer, but the 2 devices that
need to agree on flow control are the terminal and the computer -- the 2
DTEs. And those signals are not sent over the communiation link by themdoem.
However, so many devives violate the standard and use these lines for
flow control that it is very useufl to know what to do with them. The
problem comes when one device insites on using DTR (say) to indicate
buffer full while the other one uses CTS to control the transmitter. You
need a speically-wired cable in that case. Not hard to do, though.
did not do). But having the DSR signal is useful to
detect if someone=20
Are there really no DEC RS232 ports with hardware flow control. I am very
suprised...
-tony
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