Dobbertin Smart Watch

The Dobbertin Smart Watch was produced by Dobbertin Industrie Elektronik, a German company. This real time clock was relative wide spread in the 80ies and 90ies.

Technicals

The SmartWatch consists out of the RTC itself and an EPROM expansion with a lot of RSX commends. The RTC itself was inserted like an EPROM in any kind of ROM or EPROM card. Further it contains a little battery. At least one clock is still running in 2014!

This Real-Time Clock chip suffers from the Y2K bug and so should be considered worthless now. Fortunately, since 2021 we have an elegant replacement solution in the form of the Nova RTC/NVRAM expansion that is already supported in FutureOS, SymbOS and UniDOS.

Dallas Semiconductors SmartWatch

The 28pin SmartWatch (DS1216) is an adapter that can inserted in standard ROM sockets, a ROM chip can be mounted on the adapter, finally, inside of the adapter is a 16pin Phantom Time Chip (DS1315). Normal memory reads are forwarded to the piggyback ROM. After reading from a specific sequence of addresses, the ROM is disabled, and data is instead read from the Phantom Chip via 1bit databus. Writing to the Phantom Chip is done by reading from a specific sequence of addresses, too.

• DS1216-smart-watch.pdf - Dallas Datasheet for 28pin SmartWatch Adapter
• DS1315-phantom-time-chip.pdf - Dallas Datasheet for 16pin Phantom Time Chip
• DS1216-app-note-52.pdf - Dallas Application Note on SmartWatch and Phantom Time Chip

64bit packets

Accessing the RTC is done by following steps

• Read 1 or more bits (this resets the recognition pattern; best read at least 64 bits, in case the chip was in the 64-bit data read phase)
• Write the 8-byte (64bit) recognition pattern
• Read or Write the 8-byte (64bit) register data

The 8-byte (64bit) pattern/data is transferred serially, LSB first. The used bits on address and databus are:

A2 data direction (0=write, 1=read)
A0 data written to RTC, when A2=0=write
D0 data read from RTC, when A2=1=read, and only when pattern recognized

Recognition Pattern

The recognition pattern is: C5h, 3Ah, A3h, 5Ch, C5h, 3Ah, A3h, 5Ch.

Register 0..7

0  1/100 Seconds (BCD 00h..99h)
1  Seconds       (BCD 00h..59h) (Bit7=Zero)
2  Minutes       (BCD 00h..59h) (Bit7=Zero)
3  Hours         (BCD 01h..12h or 00h..23h) (Bit5=PM when Bit7=12-hour mode) (Bit6=Zero)
4  Day of Week   (01h..07h) (Bit4=Disable Reset input, Bit5=Disable OSC, stop clock) (Bit3,6,7=Zero)
5  Day           (BCD 01h..31h) (Bit6-7=Zero)
6  Month         (BCD 01h..12h) (Bit5-7=Zero)
7  Year          (BCD 00h..99h)

Pictures

The original RTC from Dobbertin.

The expanded version from dxs.

Downloads

• TIME ROM+ ROM file
• MF2_RRB.DSK - Vortex disc, containing the TimeRom+ CP/M driver

Software

• The TimeROM Software provides RSX commands to use the RTC under BASIC.
• Support for CP/M Plus is provided. The TIMEROM+.COM program sets the software clock according to the RTC. Please use the patched versions of DATE.COM, DIR.COM, SETDEF.COM and SHOW.COM (Y2K Patch).
• TFM's TIMEROM#.COM supports ROM slots 0-127 now.
• The Smart Watch is supported by FutureOS. TFM provided some routines here.
• The Smart Watch is also supported by SymbOS and is emulated in WinApe.

Links

• CPCWiki Forum thread