i did some research and collecting the roms.
so as darksoft say U45 and u46 is holding the main programm for the cpu:
ROM_REGION( 0x400000, "maincpu", 0 ) \
ROM_LOAD16_WORD_SWAP( "bpsm945a.u45", 0x000000, 0x080000, CRC(898c9515) SHA1(0fe8d7f13f5cfe2f6e79a0a21b2e8e7e70e65c4b) ) \...