On 2006-01-06, Charles Jean <alchemcj@earthlink.net> wrote:

Who's Mark?

I am familiar with the polarities and V requirements of the
"real" RS232 as shown in the example below for ASCII 65("A"):


+15V-|------<--8 character bits---->--------------
| ___ _______________ ___
| |S | | | | |
| |T | | | | |
| |A | | | | |
+3V-|--|R-|--|--------------|--|--|--------------
| |T | | | | |INDETERMINATE
| | | | | | |VOLTAGE
0V-|--|B-|--|--------------|--|--|--------------
| |I | | | | |REGION
| |T | | | | |
-3V-|--|--|--|--------------|--|--|--------------
| | | | | | |
| | | | | | | TWO
| | | | | | | STOP
| | | | | | | BITS
____|__| |__| | | | | |__| |__|__| | | |
| 0 1 0 0 0 0 0 1 0 1 1
-15V-|------LSB------------------MSB--------------

Bit width = 1/9600 seconds = 104.2 microseconds


Can someone please educate me as to what are:

1)"normal" TTL RS232 voltage levels

2)"inverted" TTL RS232 voltage levels

Thanks Mark, for clearing that up. Does this look like the proper way
to send the chip an "A", then, with the mode set at "normal"
TTL(0-5V)? What are the indeterminate voltage limits? Any need for a
delay prior to sending the next character"?

|------<--8 character bits---->--------------
+5V_|___ ___ ___ ______
| |S | | | | | | | | | | |
| |T | | | | |2 STOP
| |A | | | | |BITS
+2.0V-|--|R-|--|--------------|--|--|--------------
| |T | | | | |
| | | | | | |INDETERMINATE
| |B | | | | |VOLTAGE
| |I | | | | |REGION
| |T | | | | |
+0.8V-|--|--|--|--------------|--|--|--------------
| | | | | | |
| | | | | | |
| | | | | | |
| | | | | | |
0V_| |__| |--|--|--|--|--| |__| | |
0 1 0 0 0 0 0 1 0 1 1
LSB MSB

Bit width = 1/9600 seconds = 104.2 microseconds

"Grant Edwards" <grante@visi.com> wrote in message
news:11rrh9c2vse2h8d@corp.supernews.com...
On 2006-01-06, Charles Jean <alchemcj@earthlink.net> wrote:

Who's Mark?

[snip]

"techie_alison" wrote:
"Grant Edwards" wrote ...
Charles Jean wrote:

Who's Mark?

[snip]

Space's brother ?

Charles Jean wrote:
Thanks Mark, for clearing that up. Does this look like the proper way
to send the chip an "A", then, with the mode set at "normal"
TTL(0-5V)? What are the indeterminate voltage limits? Any need for a
delay prior to sending the next character"?

|------<--8 character bits---->--------------
+5V_|___ ___ ___ ______
| |S | | | | | | | | | | |
| |T | | | | |2 STOP
| |A | | | | |BITS
+2.0V-|--|R-|--|--------------|--|--|--------------
| |T | | | | |
| | | | | | |INDETERMINATE
| |B | | | | |VOLTAGE
| |I | | | | |REGION
| |T | | | | |
+0.8V-|--|--|--|--------------|--|--|--------------
| | | | | | |
| | | | | | |
| | | | | | |
| | | | | | |
0V_| |__| |--|--|--|--|--| |__| | |
0 1 0 0 0 0 0 1 0 1 1
LSB MSB

Bit width = 1/9600 seconds = 104.2 microseconds

No delay should be required.

-- Dave Tweed
___

"Jim Thompson" wrote ...
"techie_alison" wrote:
"Grant Edwards" wrote ...
Charles Jean wrote:

Who's Mark?

[snip]

Space's brother ?:-)

ROTFL! )

(But likely lost on the younger crowd.)

Richard Crowley wrote:

"Jim Thompson" wrote ...
"techie_alison" wrote:
"Grant Edwards" wrote ...
Charles Jean wrote:

Who's Mark?

[snip]

Space's brother ?:-)

ROTFL! )

(But likely lost on the younger crowd.)


Yeah, they don't know what they missed by never working on the old AP
& UPI newswire KSR33 teletypes on a leased loop.

On 1/6/06 9:34 PM, in article 43BF5267.24D39FBB@earthlink.net, "Michael A.
Terrell" <mike.terrell@earthlink.net> wrote:

Richard Crowley wrote:

"Jim Thompson" wrote ...
"techie_alison" wrote:
"Grant Edwards" wrote ...
Charles Jean wrote:

Who's Mark?

[snip]

Space's brother ?:-)

ROTFL! )

(But likely lost on the younger crowd.)


Yeah, they don't know what they missed by never working on the old AP
& UPI newswire KSR33 teletypes on a leased loop.

Or the models 14, 15 and 19 that were even before your time. They seemed
hi-tech at the time. My first one at home was a 14 with the range crank on
top, front. It came from a Telco Toll office.

On 1/6/06 9:34 PM, in article 43BF5267.24D39FBB@earthlink.net, "Michael A.
Terrell" <mike.terrell@earthlink.net> wrote:

Yeah, they don't know what they missed by never working on the old AP
& UPI newswire KSR33 teletypes on a leased loop.

Or the models 14, 15 and 19 that were even before your time. They seemed
hi-tech at the time. My first one at home was a 14 with the range crank on
top, front. It came from a Telco Toll office.

"Chuck Harris" wrote ...
The wire services used 5 bit machines, such as the model 15, 19, and
28.
The model 15 is what all of us old fogies remember as the intro to US
nightly
TV news. They always started and ended with a few seconds of model 15
teletype chatter... Walter Cronkite would fill in the time in between.

We would have been better off with 28:30 of TTY SFX. :-)

I just heard a radio spot the other day with TTY SFX in the
background and the announcer using his best "radio announcer"
voice (a parody on news-flash style). It was interesting that the
sound of the old TTYs is so anacronistic these days.

I was a college freshman running the college radio station
solo when they made the mistake and sent the REAL missle
attack message over the wire (instead of the regular sunday-
morning test tape). That gave us a morning of excitement.

On 1/6/06 9:34 PM, in article 43BF5267.24D39FBB@earthlink.net, "Michael A.
Terrell" <mike.terrell@earthlink.net> wrote:

Richard Crowley wrote:

"Jim Thompson" wrote ...
"techie_alison" wrote:
"Grant Edwards" wrote ...
Charles Jean wrote:

Who's Mark?

[snip]

Space's brother ?:-)

ROTFL! )

(But likely lost on the younger crowd.)


Yeah, they don't know what they missed by never working on the old AP
& UPI newswire KSR33 teletypes on a leased loop.

Or the models 14, 15 and 19 that were even before your time. They seemed
hi-tech at the time. My first one at home was a 14 with the range crank on
top, front. It came from a Telco Toll office.

I'm the OP of this thread and would like to thank everyone for such a
voluminous and knowledeable response! For those that wanted to know,
the chip is the SV2000 video interface chip from
http://www.speechchips.com. It inputs serial ASCII data and converts
to an RS170 composite video encoded stream. It is supposed to give a
9 line X 16 character display, with a standard ASCII font as well as
user-defined fonts. Control commands are preceeded by ASCII 27(ESC).
It has been marked down from $20 from $10. I already had a portable
BW TV with a composite video input, so I thought I might try it. By
bit-banging I wouldn't use the precious single UART of my uC, and only
one of its output pins.

As you can see from the data sheet, the connection on pin 6 allows for
either "normal" or "inverted" TTL levels to be used. I think I could
have saved lots of confusion by rephrasing my question to: "What's the
idling voltage of normal and inverted TTL serial lines?" I can write
the program to have the line at pin 3 idle at either 0 or 5 volts, and
I had a 50-50 chance of having pin 6 wired correctly. Just lazy
again. Sorry if I caused any trouble.