>The R-register is increased after every refresh, for old memory-modules.
>They had to be refreshed in parts. For the module, to see which part would
>be refreshed, the code would be on the data-bus (or the lower 8 bit of the
>address bus, I don't remember). This is what the Refresh-register (R for
>short) is used for. I believe a refresh is done once every machine cycle,
>so you can calculate the value of R. I don't see the use of setting the
>R-register, except if you program a Z80 (not a MSX) without memory and you
>need just one more byte. If you use it as memory, you really have to watch
>your timing very much. Mostly it is used as a random generator (or as a
>part of one), since in a normal program (with interrupt and so on in the
>loop) it will be random what's the value in it. I use it in a game I want
>to sell in Tilburg... There is one problem about it, though. The Z380,
>which will most probably be the CPU in the next MSX (if there will be
>any), does not change the value of R. This means that programs like my
>game wouldn't work (my game would just be very boring, actually. It would
>be almost impossible to loose). Of course this would not be the problem of
>the program, but the problem of the computer... If it wants to call itself
>MSX, it has to be compatible with the older ones. I don't think it will
>be, and I don't think anybody really cares. You could put a Z80 in it if
>you really want to. Those things are almost free these days (3US$ or
>something).
I know ANMA has used the Refreshregister in their SOURCE OF POWER-demo to
generate randomstars......
Anne de Raad
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