I can recommend C65 and M65 emulator XEMU https://bintray.com/lgblgblgb/generic/xemu#files
It's not finished project, but if you missing hardware, helps - even better than MESS.
To code:
NOP are required for timing after CPU activation, so when is CPU switched on, needs sync.
SCPU optimization: If anybody uses CP/M cartridge with SCPU, in turbo mode switch fails, req'd is slow down to 1/2MHz. In code is also checked status before switch, so if was turbo on, it turns it back...
Miro
:: @MIRKOSOFT added on 02 Sep ’17 · 04:54
I forgot:
I wrote that you haven't hardware...
Ask what to test, I do it - I have N4DDR with M65 bitstream indirect by Paul, can't share.
Miro