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PostPosted: Sat May 05, 2018 5:29 am 
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Joined: Sun Jan 07, 2018 2:23 am
Posts: 6
Hey,

I was looking at Colordreams BC6 and REVC PCBs and I found the connections to be as follows:
Code:
                                  .---\/---.
                    CPU R/W (n) - |01    20| - +5V
                    PRG A15 (r) - |02    19| - CHR A16 (r)
                     PRG D0 (s) - |03    18| - PRG D7 (s)
                     PRG D1 (s) - |04    17| - PRG D6 (s)
                    PRG A16 (r) - |05    16| - CHR A15 (r)
                          [CIC] - |06    15| - CHR A14 (r)
                     PRG D2 (s) - |07    14| - PRG D5 (s)
                     PRG D3 (s) - |08    13| - PRG D4 (s)
                          [CIC] - |09    12| - CHR A13 (r)
                            GND - |10    11| - /ROMSEL & PRG /CE (s)
                                  `--------'
                                     '377


I found the connections to be consistent between BC6 (128Kb/128Kb) and REVC (64Kb/64Kb) but I have not been able to get hold of REVA/B boards
and I was wondering if the consistency continues down? (64Kb/32Kb, 32Kb/32Kb, 32Kb/16Kb, 64Kb/16Kb)

When i talk about consistency, i mean that the 377 connects the 1D-8D and 1Q-8Q to the same pins on PRG/CHR even if the size is lower.


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PostPosted: Sat May 05, 2018 10:27 am 
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Joined: Sun Apr 13, 2008 11:12 am
Posts: 7210
Location: Seattle
That's often the case. It's easiest to get only one PCB made and use the size of ROMs appropriate for the game. (Nothing bad happens if the outputs of the latch aren't connected to anything, regardless of whether that's because there's no trace, or the input on the ROM is NC)

You can get pictures of the REVA and REVB boards via NEScartDB. (By the sizes of games present, they're both wired for at least 64/64)


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PostPosted: Sun May 06, 2018 12:17 am 
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Joined: Sun Jan 07, 2018 2:23 am
Posts: 6
Ok that was what i though. It make sense for an unlicensed company to do it that way.
Thanks for the links, i will definitly retrace the traces that should be connected to see if it is so.

If I understand you correctly, it doesnt matter if, for example, 377 16 Q6, is connected to a CHR ROM where there is no CHR A15 (32kb ROM). Does that man that i could, in theory, move chips from a 32kb/32kb board to a 64kb/64kb board if the connections to the '377 are the same, eg in this case from REVA board to a REVC board, without modifications to the board?

Sorry for all the questions, but I am just trying to wrap my head around how the flip flop works in discrete mappers.


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PostPosted: Sun May 06, 2018 9:22 am 
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Joined: Sun Apr 13, 2008 11:12 am
Posts: 7210
Location: Seattle
chimaera wrote:
If I understand you correctly, it doesn't matter if, for example, 377 16 Q6, is connected to a CHR ROM where there is no CHR A15 (32kb ROM). Does that man that i could, in theory, move chips from a 32kb/32kb board to a 64kb/64kb board if the connections to the '377 are the same, e.g. in this case from REVA board to a REVC board, without modifications to the board?
Yes, that is exactly what it means ... and assuredly why Color Dreams did that.


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PostPosted: Sun May 06, 2018 10:20 am 
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Joined: Sun Jan 07, 2018 2:23 am
Posts: 6
Thank you very much for clearing that up for me!


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