The ASIC has the RTC built into it. You need to power the ASIC to get the RTC to run when the game is turned off. The ASIC consumes too much current for a lithium coin cell. CR2032 would last a year or so before it dies based on some standby current readings german pinball posted.
The best idea I came up with, and people still said it was a dumb, was to use NVRAM and a 5v wall wart to power the ASIC when the game is off.
https://pinside.com/pinball/forum/topic/wpc-real-time-clock-and-nvram-solution
Worked fine. I had Johnny Mnemonic setup like that ^
Auckland, NZ
Rancho Cucamonga, CA
