Real Time Clock/Calendar Card

Why this card and not one of numerous others? Well, this card is the only one I managed to write working, useful software for :-).

Board RTCC Card

The Real Time Clock Calendar Card board is designed for usage with the "Utrecht-bus" an Eurocard based extension for the TRS-80 model 1 bus which was used by members of the Dutch TRS-80 User Group, once the largest single computer club with 4000 members. The Utrecht bus added buffering and a direction reversal signal, making it very similar to the Model 3 bus.

Schema RTCCC Schema

The RTCC is based on the MSM5832 Real Time Clock Calendar chip. Bus interfacing is done with a 8255 PPI chip. The schema and board design are by "JJ. TL."

I bought the RTCC card as a board and description. The description also contained the listing of an assembly program used with the board. Some lines were missing from my copy and the remainder was so unclear and seemingly overcomplex to me, that I decided to write my own program. Having very limited assembly programming experience, it took me quite a while. The set was bought in 1985, the software completed in 1989. A small exuse is that I got the 5832 datasheet only in 1988 :-).

Instead of writing a stand-alone program to control the card, I decided to leave as much as possible to the DOS clockroutines. So the routines just copy the DOS clock values to the RTCC card (SETRTCC.ASM) or back (SETCLK.ASM).

The Component Layout and board masks are also available.

Last update: 2003-12-25