MV1B UniBIOS unable to set calendar?

[Kujako]

I have a MV1B I'm tinkering with, and I've found I can't set the calendar. Soft dip settings save just fine, so backup RAM is good and getting power. But the calendar shows 00/00/00 00:00:00. When I go in to set it, I can change the values using A/B but when I press D to save the changes it reverts back to all zeros.

Not seen this before, so a new and exciting failure of some sort. Any ideas?

 

[nem]

RTC is busted?

 

[Ryoandr]

Check activity on test point TP1 (scope or logic probe), it goes high / low every second.
If it doesn't, well there are several points to check :

RTC power line
32.768 khz crystal, should be pulsating on at least on one leg
crystal capacitors C2 C3
RTC itself, NEC µPD4990

 

[Kujako]

Check activity on test point TP1 (scope or logic probe), it goes high / low every second.
If it doesn't, well there are several points to check :

RTC power line
32.768 khz crystal, should be pulsating on at least on one leg
crystal capacitors C2 C3
RTC itself, NEC µPD4990

Off at an attempted vacation, will take a look when I get back. Thanks!

 

[Kujako]

Check activity on test point TP1 (scope or logic probe), it goes high / low every second.
If it doesn't, well there are several points to check :

RTC power line
32.768 khz crystal, should be pulsating on at least on one leg
crystal capacitors C2 C3
RTC itself, NEC µPD4990

Confirmed 1hz signal on TP1. So getting the expected activity. Softdip values still there, still having the same issue with the calendar resetting to 00/00/00 00:00:00 when I press (D).

Kinda stumped. Everything seems fine other than this, and the calendar doesn't really matter. But this is super weird. It's not that it isn't keeping time, it's that the time isn't being stored. So an issue with the BIOS? Not sure how I would go about the calendar memory read/write diagnostics. Could go into the memory view of UniBIOS and check the relevant addresses... but don't know that it would tell me anything.

https://wiki.neogeodev.org/index.php?title=BIOS_RAM_locations#Calendar_Related

I guess that if I see the correct values there, it would tell me that it's a read not a write problem.

Edit: not seeing a reasonable way to scroll to those memory locations in the standard stack viewer. Will try the 240p test suite.

 

[Kujako]

Need a sanity check... using the 240p test suite and a board that is working correctly (I can set the date/time) I'm looking for the 10FDD-- memory region for the date (set to today). But I'm not seeing it. 10FDD2 should be set to the two digit year '23' (17 in HEX). But not seeing anything like that. Need to figure out how to read this before trying on the board with the problem.