OSWORD &0F

OSWORD &0F (15): Write Real-Time clock

On entry:
 XY?0=length of data at XY+1
 XY?0=3   Set alarm XY+1=3-byte BCD alarm block
 XY?0=5   Set from  XY+1=5-byte centisecond time
 XY?0=7   Set from  XY+1=7-byte BCD date block, year 1980-2079
 XY?0=8   Set from  XY+1=8-byte BCD date block with century
 XY?0=8   Set from  XY+1="hh:mm:ss"
 XY?0=11  Set from  XY+1="dd mmm yyyy"
 XY?0=15  Set from  XY+1="DDD,dd mmm yyyy"
 XY?0=20  Set from  XY+1="dd mmm yyyy.hh:mm:ss"
 XY?0=24  Set from  XY+1="DDD,dd mmm yyyy.hh:mm:ss"

The caller should simply store the length of the passed data at XY?0 and store the passed data at XY+1. The caller must not put any interpretation on the data and length it passes, that is entirely the responsibility of the code that implements the call, not the caller.

On exit:
 The only defined exit state is that unsupported calls should leave the control
 block unchanged, and known implementations leave the control block unchanged
 after successful calls. Known implementations also leave the control block
 unchanged after unsuccessful calls.
 
 An appropriate extention would be for supported calls to modify the returned
 control block if passed invalid data, such as 8,"99:88:77" which is an invalid
 time.

Data format

The date string format is "DDD,dd mmm yyyy.hh:mm:ss". The punctuation is normally
irrelevant, the position of the component values is fixed.

7-byte BCD date block format:
 +0 year    &00-&99 year is 1980-2079
 +1 month   &01-&12
 +2 date    &01-&31
 +3 day     &01-&07 Sun-Sat or &00 for unsupported
 +4 hour    &00-&59
 +5 minute  &00-&59
 +6 second  &00-&59

8-byte BCD date block format:
 +0 century &00-&99
 +1 year    &00-&99
 +2 month   &01-&12
 +3 date    &01-&31
 +4 day     &01-&07 Sun-Sat or &00 for unsupported
 +5 hour    &00-&59
 +6 minute  &00-&59
 +7 second  &00-&59

3-byte BCD alarm block format:
 +0 hour    &00-&59 or &C0-&FF for 'any'
 +1 minute  &00-&59 or &C0-&FF for 'any'
 +2 second  &00-&59 or &C0-&FF for 'any'

Calling from BASIC

 REM X%=>control block, Y%=X%DIV256
 REM T$=string
 :
 X%?0=LEN(T$):$(X%+1)=T$
 A%=15:CALL OSWORD

Implementation

On a system without a Real Time Clock, the MOS passes OSWORD 15 to sideways ROMs for support. Implementations should ignore unsupported subcodes and pass them on. Writing invalid data should be silently swallowed, what the implementation does with invalid data is implementation specific.

Master MOS

The Master MOS 3 and MOS 4 implements subcalls 8,15,24. Unimplemented subcalls are swallowed and not passed on.

Master Compact

The Master MOS 5 passes all calls to sideways ROMs.

SoftRTC

The SoftRTC module stores the time and date with the system TIME timer. It implements subcalls 7,8,11,15,20,24. The SoftRTC module included in HADFS sets the date with *SETDATE. Unimplemented subcalls are passed on.

RISC OS

Implements subcodes 5,8,15,24. The century is read from the system configuration.

Suitable possible extensions

Calls to OSWORD &0F are simply length,string, so additional calls can be implemented for suitable parameters. These are some possibilities.

  1,nn             - ?
  2,nn,nn          - ?
  4,"yyyy"         - set year
  6,"xxxxxx"       - ?
  9,"xxxxxxxxx"    - ?
 10,"A=hh:mm:ss"   - set alarm

Notes

Have not yet found information to document implementations supporting turning alarm on/off, and reading alarm setting.

See Also

• OSWORD &0E
• https://mdfs.net/Docs/Comp/BBC/Osword/RTCOswords

Jgharston 12:57, 26 May 2009 (UTC) Jgharston (talk) 00:16, 7 January 2023 (CET) Jgharston (talk) 21:04, 7 February 2023 (CET)