This is a simple Game Boy ROM that lets you play around with the Real Time Clock registers, originally developed to debug the implementation used by the EZ Flash Junior.
You can grab a ROM on the releases tab.
At the top, the current values of the RTC registers are shown, starting with
DAY_HIGH ($0C) on the left. They are updated every frame (which means the
bank select register is cycled 60 times a second), but by default you have to
latch the registers manually.
SELECT toggles between writing values and latching the registers (indicated by the arrow on the left).
When writing values:
- UP/DOWN to change the value
- LEFT/RIGHT to change the address and the digit you're modifying
- A to write the byte
When latching:
- LEFT to write a 0
- RIGHT to write a 1
- START to switch to automatic latching. It will get disabled once you press LEFT or RIGHT again.
The value last written to the latch register is highlighted.