I just looked at the schematics of the turbo r and it looks like NMI is connected to VCC.

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I just looked at the schematics of the turbo r and it looks like NMI is connected to VCC.

Oh, yes. It is a feature for developers. To use it you must remove this Vcc connection and connect it to the appropriate S1990 pin.

I think debugging features should be implemented in the VHDL of s1990 of 1chipMSX... when it will work in TurboR mode
In my wishlist:
- hw breakpoint(s) on read, write or fetch from a 16 bit address
- when hw breakpoint is asserted, cpu should not "call" 0x0066 (as NMI would) but should call a user programmable address (I would set it on page 3 which should never change so should be always available and coming from main mapper)
Can somebody implement these in actual 1chipMSX firmware? Alex... caro... HRA!... KdL... is anybody interested/listening