SYMBiFACE II uses a Dallas DS12887A RTC chip. [https://www.cpcwiki.eu/forum/amstrad-cpc-hardware/real-time-clock-board/msg249380/#msg249380 Source]
According to This chip is a modernized version of the datasheetMC146818, this has 113 bytes RAMthe original RTC chip used in the IBM PC/AT. It's ram inside the deviceincludes a built-in battery and crystal. Century register doesn't exist on this particular modelIt is a [[PC compatible RTC chip]] and is programmed in the same way.
Both are [[PC compatible RTC It has 14 bytes of registers and 114 bytes of battery-backed static RAM. Century register doesn't exist on this particular model. The chip]] also provides time-of-day alarm, three maskable interrupts with a common interrupt output, and are programmed in the same waya programmable square wave output.
Therefore do not rely on a specific amount of RAM inside the RTC chipIt has hardcoded daylight saving adjustment, 24-hour and 12-hour format modes, binary and BCD format modes.
== Ports ==
<pre>
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 ??01-07#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 millennium 19 or 20 (bcd or binary)#?? memory all other registers from #0E to #7F can be freely used as persistent memory
</pre>
* Note: Register B, Bit 2 allows to select BCD or Binary mode for registers 0..9 (however, this does - of course - not affect RAM location 32h) == Bugs == * Register 32h is meant to contain the Century (not Millennium)* Register 32h can be only '''either''' bcd '''or''' binary (not both)* Register 32h documentation does not specify whether it shall be BCD or Binary* Register 32h source code supports only two centuries (19 and 20) this is probably due to misunderstanding the RTC chip datasheet (which sorts of suggests the 8bit RAM location can contain only two different values, which is total nonsense)* Whether other RAM locations are reserved for whatever purpose (like info about connected 40/80 track drives) is unknown. See note 1 please.* The RAM capacity is 50 bytes: register 0Eh..3Fh (although SYMBiFACE II is incorrectly advertised to have 128 byte persistent RAM)
Note 1: In the discmag [[Future View IV]] a proposal is given how to use the non volatile RAM of the SYMBiFACE II and the CPC-Booster+.
== Software ==
The RTC of the SYMBiFACE II is supported by* [[FutureOS]] (binary and BCD mode)* , [[SymbOS]] (binary mode), [[HDCPM]].
== See also ==
