Dumitrache, Nicolae

NextZ80

1. NMI sticky (SNMI) is not correctly implemented. Currently, NMI signal should be active until FNMI is activated, but FNMI is internal signal and cannot be analyzed by external modules. Moreover, one-clock NMI signals may be ignored. Fix is simple: just replace condition `(SNMI & !FNMI)` by `((NMI|SNMI) & !FNMI)` and add `SNMI <= 0;` to the if body.
2. No NMI acknowledge. Regarding to Zilog Z80 specification NMI acknowledge cycle is looks like generic memory read, so MREQ should be activated on first NMI processing stage.
3. NextZ80 jumps to address 0x00 instead of 0x66 after NMI accepting. I cannot understand why it happens.

NMI not work

I have added support for eZ80 instructions to your core (all instructions which works in Z80 mode of eZ80). Processor works perfectly (without any bugs for instructions which I use). Basically I start my changes on 7th SVN revision of your project. Later I backport all your later changes.
There is fixed bug with R register which was kept unchanged while processor executing HALT instruction (original Z80 executes HALT instruction as infinite NOP instruction, so R changes each 4 clocks).
Sources you may download from here: https://yadi.sk/d/417xl6Gn5fE0LQ

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NextZ80