ATS vs 3.0 Release Notes

This new release of the BBC's Advanced Teletext System ROM for the Acorn
teletext adaptor has been produced in response to the demand from owners
of the Master 512 for a version that will allow them to access the IBM
programs now being broadcast.  The opportunity has been taken to
incorporate a number of other improvements:

 1)  *DISPLAY now copes with out of order rows (as produced by *DATA now
     that row 27 is transmitted immediately after the header).

 2)  The Error number produced by Escape has been corrected to 17
     (previously this was 27).

 3)  *DATE has been re-coded to give the correct date during a leap year.

 4)  The Date and Time Osword calls (7A:21 and 7A:22) now have a Carriage
     Return at the end of the parameter block,  so the user no longer has
     to 'POKE' this in before reading the result string.

 5)  The Hamming decoding command (Osword 7A:25) now returns a byte with
     bits 4 and 6 set (&5n) if a single bit error has occurred.   Previous
     versions of the ROM had bit 6 set (&4n),  although the manual says it
     should be bit 4 (&1n).  Programs will now be able to detect such an
     error, whichever bit they look for.

 6)  Two new Teletext Oswords have been introduced, 7A:26 and 7A:27, to
     respectively Set and Read the emulation mode  (TTX or TFS).  As with
     all the other Teletext Oswords, the first byte in the parameter block
     is the command number, ie 26 to set the emulation mode.  The second
     byte is either 42 for TTX emulation (whereby each row in memory is
     preceded by Magazine and Row number bytes),  or 40 for TFS emulation,
     which don't have these bytes, and so a block of memory may be copied
     directly to screen memory for display.


Terminal mode improvements:

 7)  When a new page number is being entered (in terminal mode),  the page
     grabber is forced into HOLD mode so that receipt of another copy of
     the old page doesn't overwrite your partial page number entry.

 8)  Rolling Headers are only suppressed if the Interrupted Sequence or
     Suppress Header control bits are set in the header, previously they
     were also suppressed if the Inhibit Display bit was set.

 9)  The Reveal function in terminal mode now uses an Escape character
     (&9B) to replace the Conceal code (&98) instead of &80.  Held
     Graphics are thus no longer disrupted.

10)  Independent Data Rows (Datacast for example) are now filtered out at
     a very early stage.  This prevents them appearing in every seventh
     row when *DATA is used, and also prevents the page buffer
     overflowing, which resulted in the bottom few lines on magazine three
     pages being lost.  Level 2 'ghost' rows  (26, 28, & 29)  are also now
     filtered out if 30 or less rows are requested (Osword 7A:7), and so
     will no longer cause problems in Terminal and Telesoftware modes.  If
     these rows are required, use Osword 7A:7 to request more than 30 rows
     be grabbed.  (*DATA selects, and will copy up to, 48 rows.)

11)  The page grabber for the NEXT page now looks for any subpage, even if
     a specific subpage is selected on the currently selected page.

12)  Row 24 is re-displayed after any operation that clears it, ie looking
     at the Status page, issuing an OS (*) command, or Saving a page.

13)  If a link is followed to a different magazine when the parallel
     transmission system is in use, the OSWORD equivalent of *MAGAZINE is
     issued so that the rolling header shows pages for the new magazine.

14)  When deciding whether or not a received page is a duplicate copy or a
     new one, the page and subpage numbers are now compared instead of the
     first six lines (256 bytes), thus differentiating between subpages
     with a common header (for example page 100 on BBC-1 and 711 on BBC-2)


A number of improvements have been made to the Telesoftware downloader:

15)  As well as the BBC catalogue from f5, the IBM catalogue is now
     available from SHIFT-f5.  The selected catalogue is identified by a
     "Loading BBC catalogue..." or "Loading IBM catalogue..." message.

16)  IBM filenames, which can be up to eight characters long with a 3
     character extension (eg DOCUMENT.TXT), are modified to suit whichever
     filing system is in use.  Any full-stop is replaced by a slash (/),
     and the name is truncated, if necessary, to 7 characters if DFS is in
     use, or 10 for all other filing systems.

     It is up to the user to ensure that where two different filenames are
     truncated to the same name, the first file is not overwritten by the
     second.  In such cases, the first file downloaded should be re-named
     on the disc BEFORE attempting to download further files.

17)  Osword 7A:24 (download file) need no longer be given the filename in
     UPPER CASE, and the file will be saved with the case as transmitted.

18)  The number of blocks received is now displayed in decimal instead of
     hexadecimal.

19)  If a file needs more than 80 Ceefax pages, there is not room on the
     screen for all the coloured blocks, and so a simple report is given
     (ie "35 out of 85 blocks received").  This  now works correctly -
     previously the program would crash with a "File open" error on
     receipt of the second page.

20)  The Telesoftware specification allows for data to be included in the
     header as well as on rows 1 to 25, but the old version of ATS ignored
     row zero for that purpose.  This has now been implemented.  The
     specification also allows for the  "total number of blocks" parameter
     and the "end-of-block" command to be optional - they now are.

21)  In 8-bit mode, if more than one file was on the same Ceefax page,
     confusion could arise as all commands were obeyed regardless of which
     file the commands were in,  thus a re-definition in one file could
     affect the others.  This has now been corrected.

22)  A new Run Length Coding command has been added to the Telesoftware
     specification. This allows very efficient coding of data where the
     same byte (or group of bytes) is repeated many times.  Most IBM files
     have several hundred nulls (&00) at the beginning,  and so these can
     now be coded in a few characters, instead of over a page that it
     would otherwise take.  Screen dumps are another example that can be
     significantly improved.  There is no difference to the final decoded
     data, but less Ceefax pages are needed, so it is quicker to download.


The accompanying ROM image should be used as a replacement for your
existing ATS ROM.  If you have the facilities to program your own EPROMS,
you can 'blow' the image into an EPROM then replace your current ROM with
the new one. Alternatively, you can keep the image on disc and load it
into Sideways RAM whenever required. Either way, you should ensure the
original ROM is removed from your machine. (*UNPLUG on a Master will
suffice.)

If you cannot program your own EPROM, and do not have Sideways RAM
facilities, a replacement ROM can be obtained. Please write to or
telephone BBCSoft for details.

13th January 1989