14 Jan
2004
14 Jan
'04
10:22 a.m.
I have a system that does an "autobaud" when you hit return to log in. If I
hook up a VT220, it works at 7/1/E, 8/1/N, 7/1/O, etc. etc. no problem. If I
hookup a Televideo 950, hitting return gets no response at all. This is NOT
a DTE vs. DCE problem, because the televideo does work with the same system
on a different type of serial port.
I was thinking something might be brain damaged with parity
generation/checking on this terminal. Is this a known issue of TV950's?
About the only way I can find out whats going on is to dig out my datascope
and see the start data & stop bits between the two when hitting return and
see what is different.
Any thoughts?
Jay West
---
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14 Jan
14 Jan
10:33 a.m.
I have a system that does an "autobaud" when
you hit return to log
in. If I hook up a VT220, it works at 7/1/E, 8/1/N, 7/1/O, etc. etc.
no problem.
That's not what I, at least, understand autobaud to mean - that's just
parity autosensing. (Autobaud, AIUI, is autosensing the speed.)
If I hookup a Televideo 950, hitting return gets no
response at all.
This is NOT a DTE vs. DCE problem, because the televideo does work
with the same system on a different type of serial port.
...on which the VT220 also works?
My guess would be that it's got nothing to do with what's on the data
pins, but rather is because one end thinks some kind of hardware flow
control is active and isn't seeing the signals saying "go ahead and
send".
I was thinking something might be brain damaged with
parity
generation/checking on this terminal. Is this a known issue of
TV950's?
I used to use tvi950s heavily, and while it was a long time ago, I
don't recall anything of the sort. Did you set the TVI to ignore the
incoming parity bits?
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10:41 a.m.
I was thinking something might be brain damaged with
parity
generation/checking on this terminal. Is this a known issue of TV950's?
About the only way I can find out whats going on is to dig out my
datascope
and see the start data & stop bits between the two when hitting return and
see what is different.
Jay, how about the handshaking configuration? --Patrick
10:44 a.m.
sorry, should have specified that.... I was using a breakout box with all
pins disabled except 2, 3, & 7. So no, hardware handshaking isn't an issue.
Jay
----- Original Message -----
From: "Patrick Rigney" <patrick(a)evocative.com>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk(a)classiccmp.org>
Sent: Wednesday, January 14, 2004 3:41 PM
Subject: RE: oddball televideo problem
---
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> I was thinking something might be brain damaged
with parity
> generation/checking on this terminal. Is this a known issue of TV950's?
> About the only way I can find out whats going on is to dig out my
> datascope
> and see the start data & stop bits between the two when hitting return
and
see what is
different.
Jay, how about the handshaking configuration? --Patrick
2:46 p.m.
You might try other keyboard characters. Basically 'autobauding' guesses
bit rate by looking at the garbage in the UART Rx buffer (and sometimes
status flags). But incorrect parity since it's on the "far" end of the
character (I think) might trump all character patterns and look the same
to the autobaid code.
On Wed, 2004-01-14 at 13:22, Jay West wrote:
I have a system that does an "autobaud" when
you hit return to log in. If I
hook up a VT220, it works at 7/1/E, 8/1/N, 7/1/O, etc. etc. no problem. If I
hookup a Televideo 950, hitting return gets no response at all. This is NOT
a DTE vs. DCE problem, because the televideo does work with the same system
on a different type of serial port.
I was thinking something might be brain damaged with parity
generation/checking on this terminal. Is this a known issue of TV950's?
About the only way I can find out whats going on is to dig out my datascope
and see the start data & stop bits between the two when hitting return and
see what is different.
Any thoughts?
Jay West
---
[This E-mail scanned for viruses by Declude Virus]
15 Jan
15 Jan
6:15 a.m.
Jay West wrote:
I have a system that does an "autobaud" when
you hit return to log in. If I
hook up a VT220, it works at 7/1/E, 8/1/N, 7/1/O, etc. etc. no problem. If I
hookup a Televideo 950, hitting return gets no response at all. This is NOT
a DTE vs. DCE problem, because the televideo does work with the same system
on a different type of serial port.
I was thinking something might be brain damaged with parity
generation/checking on this terminal. Is this a known issue of TV950's?
About the only way I can find out whats going on is to dig out my datascope
and see the start data & stop bits between the two when hitting return and
see what is different.
Any thoughts?
Jay West
I've had problems in the past with voltage levels on RS-232.
One device runs -12/+12V, the other 0/+5V, and they refused
to talk bi-directionally. Putting in a homemade level shifter
(forced the 0/+5 to -9/+9) made it work.
I think this may have been Televideo widgets to a Vax/3100, iirc.
7:52 a.m.
I've had problems in the past with voltage levels
on RS-232.
One device runs -12/+12V, the other 0/+5V, and they
refused to talk
bi-directionally. Putting in a homemade level shifter (forced the
0/+5 to -9/+9) made it work.
I think a sending device is required to swing at least below -3V and
above +3V for it to be RS-232 (though I may have the voltages wrong,
it's been a while - but I'm sure they're symmetric about 0). I ran
into this when connecting Sun keyboards to vanilla serial ports - I
found I needed a level shifter and an inverter (of course, the inverter
may be unnecessary depending on whether the level shifter you use
inverts or not). (Sun keyboards are RS-232 except for the voltage
levels in question, and possibly impedances.)
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12:08 p.m.
I've had problems in the past with voltage
levels on RS-232.
One device runs -12/+12V, the other 0/+5V, and
they refused to talk
bi-directionally. Putting in a homemade level shifter (forced the
0/+5 to -9/+9) made it work.
I think a sending device is required to swing at least below -3V and
above +3V for it to be RS-232 (though I may have the voltages wrong,
it's been a while - but I'm sure they're symmetric about 0). I ran
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days inactive
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7 comments
6 participants
participants (6)
-
ard＠p850ug1.demon.co.uk -
jwest＠classiccmp.org -
kth＠srv.net -
mouse＠Rodents.Montreal.QC.CA -
patrick＠evocative.com -
tomj＠wps.com