I'm pulling out my hair trying to access the DS12885 RTC on the MSDOS Support PCB.
The rest of the board (timer, interrupt and EPROM) appears to be functioning properly. I have not tried the mouse/keyboard section yet. I can see low pulses on Pins 14/17 as expected. I'm using the "E" command from the 8088 board for testing time/date in V10.3 of John's monitor software. When I set the time the seconds and day will program, but the hours/minutes/year/month remain gibberish. I also get errors when entering the "X" MSDOS menu - either that the RTC is stuck or that invalid BCD data exists. I've swapped TTL and DS12885. I've also changed the 32.768khz xtal. When I scope pins 2/3 on the DS12885 (XTAL) I can see somewhat noisy pulses. Would the DS12885 at least store the date if the xtal isn't oscillating properly? It looks like the RTC shares most of the same address/data circuitry with the other sections. The 8088 has a 8 mhz clock, could speed be an issue? Any thoughts or hints appreciated! - Gary -- You received this message because you are subscribed to the Google Groups "N8VEM-S100" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
