Talk:S-1990

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[edit] About the manufacturing origin of S1990

The S1990 LSI was made by NEC. It is not same from shape of Toshiba's LSI package. And the name of only 'System LSI',not 'MSX-ENGINE'. MSX-ENGINE were 'T9769(MSX-ENGINE2)' or 'T7775(MSX-ENGINE)'. These were made by Toshiba. Because the LSI were marked 'Toshiba'. It is same to the LSI package shape of Toshiba. ･･･ The name of 'Engine' is given only to LSI equipped with CPU. CPU is not included in S1990. Yaca2671 04:53, 22 August 2007 (UTC)

• The following are examples of LSI package of NEC.

This is an example concerning LSI package of NEC. Please compare it with the shape of S1990 paying attention to the manufacturing lot number mark and the package shape. [[1]] Yaca2671 09:43, 22 August 2007 (UTC)

Okay, I researched this a bit an I am now convinced that:

• The chip was made by NEC, at least made in the same factory as the NEC chip shown.
• The chip was a "turboR bus controller", and did not itself contain neither a Z80 nor a Z800 CPU, so it was not a full "MSX-ENGINE".

I will make the necessary fixes.

Thanks Yaca2671, for this info.

P.S. I am still unsure whether the S-1990 was only used together with a R800, OR together with BOTH a R800 AND a separate (real) Z80 CPU.

I know the the R800 also can emulate a Z80, but several sources talk about the turbo R having both a R800 AND a Z80 CPU chip.

Perhaps the z80 emulation of the R800 was not good enough, and a real Z80 was needed also?

Yaca2671, maybe you can say something about this? Mahjongg 01:16, 23 August 2007 (UTC)

I also tried to use the Altavista web translate function to translate the explanation of the debug functions from the Japanese Wikipedia entry of the S-1990. I hope I understood everything correctly, please correct me if I'm wrong. Mahjongg 10:43, 23 August 2007 (UTC)

Okay, I did some more detective work, and found out the Turbo R also uses a T9769 MSX-Engine, which has a Z80 inside, and that the R800 in fact does -not- emulate a Z80. That explains a lot. So I totally revised the article. Mahjongg 12:11, 23 August 2007 (UTC)

I think that I should not write the function for S1990 not to have. For instance, S1990 have not include the PSG and VDP. They are thought that it is necessary to move the page of each chip. However, I think that describe the content of controlling the access of PSG and VDP by the Z80 bus emulation when R800 operates. S1990 controls these chips.

about the breakpoint if the pause key will push ,the user program break and jump to the debugging monitor. I do not understand whether processing moves to the user's program if the pause key is pushed again after it jump to the debugging monitor. I think so it depends on the design of the program of the debugging monitor.
Thanks.Yaca2671 21:57, 24 August 2007 (UTC)

Perhaps the part of the article that mentions the PSG and VDP article was not clear enough. I did not claim (anymore) that the S-1990 included these functions, only that the S-1990 controls access to them. I somewhat improved the article to reflect this fact.

I also changed the pause key function. However, this functionality does not seem to be a function of the S-1990 chip, but only of the Debugger software. Or I am still missing something.

I do not see any use for the S-1990 chip for this function, when simply pressing a button jumps to the debugger. But perhaps the "pause key" is directly connected to the S-1990 chip, and is not simply part of the normal MSX keyboard logic? In that case it makes sense to list it as a "hardware feature".

I assume the debugging software is contained inside a ROM of the Turbo R?

Almost all debuggers allow returning to the main program, otherwise a debugger would have very little use. Mahjongg 21:32, 24 August 2007 (UTC)