Still working on it (try #3)

A project log for Save RAM hack for NEC handheld consoles

Adding same RAM support to TurboExpress and PC Engine GT

killuakillua 06/01/2021 at 05:390 Comments

Another update: I discovered 2 of the address lines were flipped somehow. Corrected and reuploaded the Eagle files and gerber files.

I also modified the proto board by swapping the 2 reversed address lines.  I am still not getting it to work at all.

I am going nut!!!  I've checked and rechecked all the pins from the original Tennokoe, rechecked that they all were correct, all connected with SRAM as well.  Games still reports no save support at all.  I've looked at the schematic of TurboGrafx-16, there is no buffer chip or additional parts between cart pins and expansion pins, both sides are wired straight through.

One thing to note though if you are trying this, there is one more thing I forgot to mention.   Tennokoe II has CDD pin on expansion port pulled to ground. They are floating high when there's no device connected to the system.  CDD pin is not present on cart slot and aren't used on TurboExpress or PC Engine GT. You need to find pin 30 of HuC6280 CPU (the chip one closest to cart ribbon cable) and lift it then short it to ground.  The RF shield hole nearby is grounded and would work with a short jumper wire.