I think Zozo was only wishing for future enhancements of the interface.
We know already that first you must work on the original MSX protocol.
But.... it would be great to change settings to 10Mhz Z80 inside the MCU programming rather than on the driver, because that wastes less time on the MCU and on the Enterprise side. Faster Z80 implies longer delays on the driver, and all that is lost in processing time.
And then, I think a direct selection of the processor velocity could be made with the spare Data-Out pin at the serial port. The underused serial port loses its few use when changing the processor rate, as it changes the software fixed bit-rates.
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Now I understand you when you talk about interrupts, but sorry, I can't aid you on that. I'm not really a programmer, only a enthusiast of computers...
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And talking about programming, the actual driver still doesn't read the additional two Bytes(four nibbles) of the wheel and spare buttons. I think that better we wait until Prodatron implements them on the Enterprise SymbOS port.
Also, the actual driver only reads and stores the value of the main(left) mouse button. The two principal buttons are on the same row, so they can be read at the same time. But the driver hasn't a system variable to store its value.
I don't know still how adding a system variable can be done... May be Zozo can fix the driver? and if so, we also need space for the three spare buttons and wheel information. The PS/2 protocol only have four bits(Z) for the wheel information, but the new MSX protocol returns a complete byte. Then we can perfectly take the four lower Z bits without losing information.
I think we only need one system variable for storing the four buttons state on 4 bits and the wheel on the remaining 4 bits.