Early Joy Van/Idea-Tek/TXC Mappers
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Author:  MLX [ Mon Dec 18, 2017 12:45 pm ]
Post subject:  Re: Sachen TCU-02 (Mapper 136)

Seems like I have to use my continuity meter? Can one point which pins specifically should be checked?

Author:  NewRisingSun [ Mon Dec 18, 2017 12:48 pm ]
Post subject:  Re: Sachen TCU-02 (Mapper 136)

Pin 27 of the CHR chip (right chip, top row, second pin from left) should be connected to pin 22 or 23 of the ITC IC.

Author:  MLX [ Mon Dec 18, 2017 2:41 pm ]
Post subject:  Re: Sachen TCU-02 (Mapper 136)

It is pin 22.

Author:  krzysiobal [ Mon Dec 18, 2017 2:48 pm ]
Post subject:  Re: Sachen TCU-02 (Mapper 136)

Image Image Image

Author:  NewRisingSun [ Mon Dec 18, 2017 3:04 pm ]
Post subject:  Re: Sachen TCU-02 (Mapper 136)

Well, I only got pin 8 wrong and gave up on pin 18, so I guess I did not do too badly for an amateur. Thanks, everyone. We also have the PCB images of 1991 賭馬 Racing (Enjoyable Horse Racing), Mapper 172. The bankswitching code is very similar, so the IC should be functionally similar, but comes in an 28-pin rather than a 24-pin package. But that's for another day (or week, or year). ;)

lidnariq wrote:
pin 22 (had it not been defective) would have relayed values from pin 8 (or maybe pin 9?).
If anything, it would have to relay the inverse of Pin 9 (D3), and while that one may work for F15 City War and Puzzle, at least as far as I have played, it certainly fails for 小瑪琍 (Xiǎo Mǎlí). The "inverse XOR value" story matches our results with the dumping script as well as the game code.

Author:  NewRisingSun [ Sun Dec 24, 2017 1:45 pm ]
Post subject:  Re: Early Joy Van/Idea-Tek/TXC Mappers

And since it was so much fun, here are PCB shots of Mapper 136 (Mahjong Trap) and Mapper 172 (1991 Duma Racing). These use a custom IC that is functionally similar to the beloved TXC 24-pin IC, except that it comes in an 28-pin package, having six instead of four CPU (data input) and data output pins. (Although if I understood lidnariq correctly, the 24-pin IC could have as many as six CPU pins connected as well, so I wonder which other four pins' function is missing.) Mapper 172 seems similar to Mapper 136 except that the custom IC is mounted upside down.

Mapper 136 (images from Pepper-98):
MahjongTrap-Front.jpg [ 1.28 MiB | Viewed 166 times ]

MahjongTrap-Back.jpg [ 1.29 MiB | Viewed 166 times ]

Author:  NewRisingSun [ Sun Dec 24, 2017 1:48 pm ]
Post subject:  Re: Early Joy Van/Idea-Tek/TXC Mappers

Mapper 172 (images from MLX):
DumaFront.JPG [ 1.58 MiB | Viewed 165 times ]

DumaBack.JPG [ 1.62 MiB | Viewed 165 times ]
According to my trace attempt (correct me if I'm wrong), I identify the following pin functions:
Pin#    Mapper 136 connection   Mapper 172 connection   General pin function
1       PPU A13                 PPU A13                 PA13
2       CPU D5                  CPU D0                  Input D5
3       CPU D4                  CPU D1                  Input D4
4       CPU D3                  CPU D2                  Input D3
5       CPU D2                  CPU D3                  Input D2
6       CPU D1                  CPU D4                  Input D1
7       CPU D0                  CPU D5                  Input D0
8       CPU A0                  CPU A0 ($0001)          A0
9       CPU A1                  CPU A1 ($0002)          A1
10      CPU A8                  CPU A8 ($0100)          A8
11      CPU M2                  M2                      M2
12      CPU /ROMSEL             CPU /ROMSEL ($8000)     /ROMSEL
13      CPU R/W                 CPU R/W                 R/W
14      +5V                     +5V                     +5V
15                              CPU A14 ($4000)         A14
16                              CPU A13 ($2000)         A13
17      CHR /OE                 CHR /OE                 CHR /OE
18                                                      Output D5
19                                                      Output D4
20                                                      Output D3
21                                                      Output D2
22                              CHR A14                 Output D1
23                              CHR A13                 Output D0
24                              PPU A10                 PA10
25                              PPU A11                 PA11
26                              CIRAM A10               CIRAM A10
27                              PPU R/W                 PPU R/W
28                              GND/+5V                 GND/+5V
Which is odd, because that would mean that Mapper 172 has mapper-controlled mirroring, which nobody emulates. When MLX redumped Mahjong Block (Mapper 172 version), the Kazzo identified the mirroring type incorrectly, which would not happen in the case of fixed mirroring, so it's not entirely out of the question. I would not have any idea what write pattern selected the mirroring type though.

I found it easier to trace the Mapper 172 images, which is why the Mapper 136 column is rather empty. Yes, Mapper 172 has CPU D0..D5 connected in reverse, and the three Mapper 172 games indeed have code to reverse the desired six bits before they output the data to $4102.

@krzysiobal: I only noticed this now in your otherwise excellent schematic, but F-15 City War is Mapper 173, not 136. (The thread title was originally "Sachen TCU-2/Mapper 136" because that one started the thread. I have since renamed the thread title to reflect the expanded scope of the discussion.)

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