| 摘要 |
<p>PURPOSE:To end option setting operation during a program run by providing a PROM and an option ROM and writing the contents of the option ROM in option setting registers during the initialization of a system. CONSTITUTION:An option setting control circuit 3 operates to hold a signal, the inverse of RESET at a Low level and address signals A0 and A1 of the option ROM(OROM) 1 are initialized. Then when the signal, the inverse of RESET is effective, a signal, the inverse of INIT goes down to the Low level. In this state, the address signals A0 and A1 of the ORM 1 increases as a signal OPWR as an AND signal between a signal SYSCLK and the signal, the inverse of INIT rises. At the same time, the value of the OROM 1 is written in option registers (a), (b), (c), and (d) constituting an option register group 2 in order when the signal OPWR rises. Consequently, the option setting ends during the initialization of the system and it is not necessary to consider the setting of options as to a program ROM 8.</p> |
