Note: The LR35902 (GBZ80) feature was implemented, but I am deleting it because I have no plans to develop a Game Boy emulator in the foreseeable future and also because I want to prioritize ensuring the quality of the Z80.
[x] Add zexall to the standard test case
[x] Fixed refresh register update timing
According to the following document, the refresh register is done at 2 Hz after the first instruction fetch (2 Hz), so match that behavior.
I heard in a comment on Qiita that PC-8001 and MSX Z80 have such a feature. The realization of emulation is quite simple and should be implemented as an optional feature.
zexallto the standard test case