This is the documentation about the '''realtime clock''' of the [[SYMBiFACE II]] expansion card.
My (arnoldemu's) SYMBiFACE II uses a Dallas DS12887ARTC chip. Documents claim this has 128 bytes RAM[https://www. Century register doesn't exist. It's ram inside the device.The picture from the Symbos website shows a DS1287A. This has 50 bytes RAM. Century register doesn't existcpcwiki.eu/forum/amstrad-cpc-hardware/real-time-clock-board/msg249380/#msg249380 Source]
Both are This chip is a modernized version of the MC146818, the original RTC chip used in the IBM PC/AT. It includes a built-in battery and crystal. It is a [[PC compatible RTC chip]] and are is programmed in the same way.
Therefore do not rely on a specific amount It has 14 bytes of registers and 114 bytes of battery-backed static RAM inside the RTC . Century register doesn't exist on this particular model. The chipalso provides time-of-day alarm, three maskable interrupts with a common interrupt output, and a programmable square wave output. It 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 ==
* [[Media:DS12887 RTC datasheet.pdf|Dallas DS12887A datasheet]]
* [[SYMBiFACE II:RTC routines|Routines for using the RTC]]
* [[Programming:SYMBiFACE_II|SYMBiFACE II documentations]]