|Dragon's Lair Rom made for Rev. A Logic won't work on DAPHNE
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|Author:||Lord_Victorino [ Mon Jul 07, 2014 7:45 am ]|
|Post subject:||Dragon's Lair Rom made for Rev. A Logic won't work on DAPHNE|
I am making this post hoping that sometime in the future that this problem can be addressed and fixed on DAPHNE.
Serial #1 Beta Rom Set, Beta 2 Rom Set, & Rev. A - C Rom Set don't sync with the Video while playing them on DAPHNE. But this is not because they were made to only be used with a PR-7820 Laser Disc Player. Actually, it's because they were made to be used with a Rev. A Logic, only. The Rev. A Logic seems to run it's RTC Real Time Clock a bit slower then a Rev. C Logic. This is why the Roms described above don't work correctly. DAPHNE's RTC is based upon the Rev. C Logic. For these Roms to work correctly, DAPHNE will need to emulate the Rev. A RTC for these Roms to work correctly.
Below is the info. on what the differences are between the RTC of both of the Logic Boards:
In Rev. A Logic Boards Interrupts occurring at a rate of approximately 33 milliseconds are required to keep the Z80 in sync with the Laser Disc Player. The signal RTC+ (REAL TIME CLOCK) at U26-11 is a square wave with a 33 millisecond period. In Rev. C Logic Boards, U6 and U13 are cascaded to form a 16-Bit binary counter. The output of this counter circuit. U6-6 is a 33 millisecond square wave.
I'm not sure what this above means, but I believe it has something to do with why the Sync between the Game and the Video using these Roms that were made to be used with the Rev. A Logic and not the Rev. C Logic. And because DAPHNE was based upon the Rev. C Logic this is why DAPHNE does not work correctly with these Roms, either.
Tony M Victorino
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