OSWORD &0E

OSWORD &0E (14) - Reads CMOS clock

On entry:
 XY?0=function code

0 - Return clock value as string
 On exit:
  XY+0..23=CR-terminated string in form
  "Day,DD Mon Year.HH:MM:SS".

1 - Return BCD clock value.
 On exit:
  XY?0=year (&00-&99)
  XY?1=month (&01-&12)
  XY?2=date (&01-&31)
  XY?3=day of week (&01-&07, Sun-Sat or &00=not returned)
  XY?4=hours (&00-&23)
  XY?5=minutes (&00-&59)
  XY?6=seconds (&00-&59).
 
 A year value of &80-&99 represents 1980-1999, a value of
 &00-&79 represents 2000-2079.

2 - Convert BCD to string.
 On entry:
  XY+1..7=BCD value as with subfunction 1
 On exit:
  XY+1..25=CR-terminated string as with subfunction 0

3 - Return 5-byte centisecond clock value (where supported)
 On exit:
  XY?0..4=number of centiseconds since 00:00:00 01-Jan-1900

3 - Return clock value as string from file server (ANFS 4.2x)
 On exit:
  XY+0..23=CR-terminated string in form
  "Day,DD Mon Year.HH:MM:SS".

4 - Return BCD clock value from file server (ANFS).
 On exit:
  XY?0=year (&00-&99)
  XY?1=month (&01-&12)
  XY?2=date (&01-&31)
  XY?3=day of week (&00=not returned)
  XY?4=hours (&00-&23)
  XY?5=minutes (&00-&59)
  XY?6=seconds (&00-&59).
 
 A year value of &80-&99 represents 1980-1999, a value of
 &00-&79 represents 2000-2079.

? - Return BCD time/date/temperature

? - Return time/date/temperature string

Implementation

On a system without a Real Time Clock, the MOS passes OSWORD 14 to sideways ROMs for support.

ANFS

Master ANFS 4.2x implements subcalls 0,1,3,4 and calls OSWORD 14,2 to convert the result of subcall 0 and 3 to a string. BBC ANFS 4.0x and 4.1x only implements OSWORD 14,4.

The ANFS implementation fails in a predictable manner with dates after 1996. The returned date is ((year-1981) DIV 16)*16+date and the returned year is (year-1981) AND 15. The date can be repaired across the whole date range with:

 date =BCDtoBIN(returned_date) AND 31
 month=BCDtoBIN(returned_month)
 year =(BCDtoBIN(returned_date) AND &E0) DIV 2 + BCDtoBIN(returned-year) + 1900

SoftRTC

The SoftRTC module (included in HADFS) implements subcalls 0,1,2 with the date set with *SETDATE and the time being calculated from TIME.

See Also

• OSWORD &0F
• http://mdfs.net/Docs/Comp/BBC/Oswords

Jgharston 12:56, 26 May 2009 (UTC) Jgharston (talk) 06:45, 12 April 2020 (CEST)