Timefix ROM
===========

1. Purpose
This ROM allows you to set the date on the BBC Master series anywhere from
1st January 1900 to 31st Dec 2299.

2. Platform.
This ROM code is only for the Master series of BBC computers. It
communicates at a low level with the RTC IC (146818) on that platform. If
used on a BBC B it will have no effect other than appearing in the ROM
table.

3. Memory usage.
i)   Zero page &70,1 : Restored afterwards.
ii)  One page of private hidden RAM (or a low memory page if Hazel is full).
iii) CMOS RAM location 18. The top two bits are used to store the century
     19-22. This matches other date extensions.

4. Installation.
Either program an (E)EPROM, load onto a RAM/ROM board (e.g. IFEL) or load
into sideways RAM. For example:

  *SRLOAD TIMEFIX 8000 4
  *FX200,3
  BREAK

The sideways RAM option requires the above FX/BREAK sequence, which
simulates a power-on, for correct initialisation. This is related to
correct initialisation of private workspace. If you just do CTRL-BREAK
you'll likely get a "Bad sum" error and an asterisk prompt (at which you
can return to BASIC and do as above).

5. Usage
There is little to do upon activation. The TIME$ function can be used for
setting/displaying the time as usual. The *TIME command also functions as
normal. It is almost certain that the century will display incorrectly on
first use of the ROM as it will not have yet been stored in the CMOS RAM.
This can be rectified by setting the date with TIME$ or by using the
"*CONFIGURE CENTURY nn" command where nn=19 to 22. If you use *CONFIGURE
CENTURY without a parameter the century will be set to 20.

6. Technical
The ROM uses the extended vector capability, XWORDV, for OSWORD. It traps
calls to OSWORD &0E and &0F, points them to new routines which accommodate
the century information. The RTC IC is programmed directly using memory
mapped IO through SHEILA addresses. Other OSWORD commands are passed
through to the MOS.

This ROM is therefore unlikely to work alongside other software that traps
WORDV and will require reinitialisation when such software has finished
(the century, however, will still be safely stored in CMOS RAM).

In implementing the new OSWORD routines the sizes and contents of the
parameter blocks have been preserved, therefore there should be full
backwards compatibility for them. As with the original OSWORD routines,
errors in syntax will lead to commands being silently ignored.

7 Disclaimer
THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESSED OR IMPLIED WARRANTIES,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.