IC

One problem with requests like yours is the information is sparse.

What package is it in (16 pin DIP, 28 pin dip, 44 pin QFP, something designed to mount to a heat sink, etc)? It MIGHT be a µPD75402ACT, which is a NEC 4 bit microcomputer. If it is, you are either very lucky or SOL, depending on your point of view. The microcomputer's programming is on an internal ROM, without the code it's just a hunk of sand. Either the owner will have to buy herself a replacement or you must provide the action.

PlainBill

One problem with requests like yours is the information is sparse.

What package is it in (16 pin DIP, 28 pin dip, 44 pin QFP, something designed to mount to a heat sink, etc)? It MIGHT be a µPD75402ACT, which is a NEC 4 bit microcomputer. If it is, you are either very lucky or SOL, depending on your point of view. The microcomputer's programming is on an internal ROM, without the code it's just a hunk of sand. Either the owner will have to buy herself a replacement or you must provide the action.

PlainBill

In the modern age of electronics, books are obsolete. Google is your friend. There are three problems, however.

1. Googling µPD75402ACT will bring up number of sources for datasheets, as well as suppliers (chiefly in China) offereing to supply them. Those suppliers are suspect; the datasheet is 20 years old. It is likely that newer microcomputers have replaced the µPD75402ACT.
2. Not just any µPD75402ACT will work. It must have the correct firmware. The firmware was mask programmed at the time the chip was etched. There is a programmable version of the IC, it has a prom (programmable once), but even then you must have the correct firmware.
3. Assuming you can get the correct firmware and the correct IC, you mist program it. That requires a custom fixture. While the fixture may be a lot less complicated than that for a 2764 eprom, it still presents another challange.

Others may differ, but it seems like a lot of work to fix a foot massager that sells for $7 used on Craigslist!!!

PlainBill