SYMBiFACE II:Realtime clock
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This is the documentation about the realtime clock of the SYMBiFACE II expansion card.
Contents
Ports
- #FD15 (write only) register select
- #FD14 (read/write) read from or write into selected register
Registers
Number Content Values #00 actual second 00-59 (bcd or binary) #01 alarm second 00-59 (bcd or binary) #02 actual minute 00-59 (bcd or binary) #03 alarm minute 00-59 (bcd or binary) #04 actual hour 00-23 (bcd or binary) #05 alarm hour 00-23 (bcd or binary) #06 day of the week ?? #07 day of the month 01-31 (bcd or binary) #08 month 01-12 (bcd or binary) #09 year 00-99 (bcd or binary) #0A status A see below #0B status B see below #0C status C see below #0D status D see below #32 millenium 19 or 20 (bcd or binary) #?? memory all other registers can be freely used as persistent memory
Status registers
- Status A
bit0-3 [not used] interrupt frequency bit4-6 time frequency (must be 010; if not, set it to this value, otherwise the RTC will not work correctly) bit7 1 = time is being updated at the moment, so don't read it!
- Status B
bit0 1 = take summer time into account bit1 0 = 12 hours time format, 1 = 24 hours time format bit2 0 = all values in BCD format, 1 = all values in binary format bit3 1 = [not used] activate rectangle generator bit4 1 = [not used] generate interrupt after time update bit5 1 = [not used] generate interrupt if alarm bit6 1 = [not used] generate periodic interrupt (see status A, bit0-3) bit7 1 = stop time update; set this, during you update the time and reset it after the update!
- Status C
bit4 1 = [not used] interrupt has been generated because of time update (see status B, bit4) bit5 1 = [not used] interrupt has been generated because of alarm (see status B, bit5) bit6 1 = [not used] interrupt has been generated because of periodic (see status B, bit6)
- Status D
bit7 0 = battery is nearly empty, please charge or replace
