Hi Robert, if you are using 700/94 terminals (or emulating) there is a
feature called Modified Data Tag (MDT) that can be used to prevent
non-modifed fields from being transmitted. See chapter 9 - Using Forms
in the terminal manual.

More below...

Robert Pitman wrote:

> Hello all, need some help with this topic.
>
> Customer has for years been using many programs in Basic/V using block
> mode/Line setting on HP terminals. This works fine over serial lines,
> and acceptable over muxes etc.
> Now they have a connection from Oz to US, and the volume of small
> transmissions back and forth to read the individual screen fields is
> proving to be a problem, taking an unnaceptable time to do busy screens.
> We now are investigating converting to Block/Page on the screens with
> many fields that are the staple of the application, with the idea that
> we can read all unprotects back, decode the data based on knowledge of
> screen fields (separated by US chars), and extract what we need.
> I have tested things a bit, and struck some problems.
> 1. Documentation indicates that a set up of Block/Page, Inhibit DC2(G
> strap) should HomeUp cursor, send unprotects until RS (decimal 30) found
> on screen. This does NOT occur - I NEVER get an RS back. I get US
> (decimal 31) between fields as documented, but no RS. Also the data
> continues after an RS.


Sounds like you are doing some of the work that VPlus does for you. :-)
IIRC, the US and RS chars are not really on the screen, the terminal
inserts them into the data stream when ENTER is pressed.

Note that for the last Unprotected Field, there is only the RS char
after it, no US.


>
> 2. In Basic/V, reading into a 255 byte string, I only ever get 133 bytes
> back. If I issue a second read, it gets another 133 bytes (data +USs).
> Why not the 255?


Take a look at the port config. I suspect that the record width is
defaulting to 133. Or, this may be an artifact of opening the port with
BASIC/V, not sure. You may be able to set a file equate to override the
config.

FILE MYPORT;DEV=123;REC=-255


>
> 3. If I set up an SPL subroutine to call for the read, preceded by
> Fcontrol 29 (Enable transparent editing), I can get 255 bytes back, but
> it requires Enter to be pressed twice, I still dont get any RS back, and
> RS doesnt terminate the reads still.


Fcontrol 29 is User Block Mode
Fcontrol 41 is Transparent Editing Mode

What did you set as the EOR (End of record/read terminator) char?
Have you tried setting it to RS?


>
> 4. Trying to do the read without Inhibit DC2(G strap) produced some
> other undesirable effect which I forget just now - requires a double
> read, or the user to reposition the cursor, which is not firendly
> enough?
>
>
> If anybody has any ideas, please reply directly, as I am away from home
> base now.


The HP700/92 HP700/94 (terminal) Reference Manual and the Asynchronous
Serial Communications Programmers Reference Manual contain a wealth of info.


>
> Thanks for any ideas,
> Regards,
> John Pitman
>
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>
>


HTH
Erik 'I love a good serial datacomm question' Vistica

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