BiggRanger sent me schematics of a printer that uses two TMS-1025 I/O expanders; one for input and one for output. He pointed out that the MS signal controls the I/O direction. I used a PIC to control a TMS-1024 and a TMS-1025, and captured some signals with a Saleae Logic. I also captured signals while playing Tomy Break Up. And I figured out how to electronically dump the lower 7 bits of the TMS-1040 in Break Up, and they match the visual dump.