Component documentation in PDF, 122 KB, for a device numbered 23c128. By common convention a 23C part is a mask ROM, here with the number suggesting 128 Kbit, but the file gives no manufacturer in its name, so open it to verify. Such sheets give the pinout, address and data line arrangement, chip enable behaviour and timing. Use it to trace signals around the ROM, check supply, or plan replacement with a programmable part of matching pinout, after confirming the chip marking corresponds to this number.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @cyberlanelectonik. Enginerys does not host this file.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.