I haven't done much with this project for a while, apart from building some custom TCUs with special shift maps.
Somebody just sent me a new software called JECScan that can log ECU and TCU parameters, and download the ROMS to a file. It's on my website for download if anyone wants to try it.
This is currently the only windows software that can download TCU rom.
I've also got some information on communicating with the cruise control unit. It uses an older protocol designed for the L-series (Leone). It needs a modified interface and special software to communicate. I'd like to make it work just for completeness, but I don't see anybody ever using it.
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Subaru ECU and TCU Website
1992 Alcyone SVX Version L
1992 Alcyone SVX Version L
1994 Alcyone SVX S40-II
2004 Subaru Legacy 2.5 SE Sports Tourer
1996 Subaru Legacy 2.2 GX Wagon
1988 Subaru Justy J12 SL-II