Fujitsu MB8840/MB8840H Series
MB8840 is a series of 4-bit microcontrollers from Fujitsu, containing models MB8842, MB8843, MB8844, MB8846, MB8847 and MB8848. The missing numbers in that sequence are MB8840H, MB8841H and MB8845H from the MB8840H high-speed series.
The following examples exist of MB8840/MB8840H Series chips used as keyboard encoders:
|MB8841||8407||724M||Sony OA-S3400 keyboard|
Despite the MB8841 using a plus-sized DIP42 package, the OA-S3400 keyboard still requires a considerable amount of additional logic. Next to the MB8841 is an SN74150N 16-line to 1-line data selector/multiplexer; there are at least eight further chips but none of them can be identified from the photographs.