Real-Time Clock OSWORDs
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OSWORD 14 - Read RTC
 XY?0=0+n use 7-bit BCD date block
 XY?0=8+n use 8-bit BCD date block
 XY?0=0  XY?0=8   Read as 25-character string
 XY?0=1  XY?0=9   Read as 7- or 8-byte BCD block
 XY?0=2  XY?0=10  Convert 7- or 8-byte BCD block at XY+1 to string
 XY?0=3           Read as 5-byte centisecond time
 XY?0=3           Read 25-character string from file server (ANFS 4.2x)
 XY?0=4           Read BCD clock value from file server (ANFS)
 XY?0=4           Return "hh:mm:ss DDD dd-mm-yy tt",CR
                  where tt is temperature. (I2C Control ROM)
 XY?0=5
 XY?0=6
 XY?0=7

OSWORD 15 - Write RTC
 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"

String date 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 &19-&20
 +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'

Turn alarm on?
Turn alarm off?
Read alarm?