| 摘要 |
A CPU outputs address data indicating a data storing unit or an OSD-RAM to access the data storing unit or the OSD-RAM, and an OSD logical circuit sometimes accesses the OSD-RAM to display data on an on-screen display. The address data is decoded in an OSD-RAM address decoder, and a decoded signal of "0" or "1" is output to an OR gate. Also, a value "0" normally set in a 1-wait register is output to the OR gate. When the address data indicates the data storing unit, a value "0" is output from the OR gate to a bus interface unit (BIU), an access mode of the CPU is set to a no-wait access mode corresponding to a shortest cycle, and the CPU accesses the data storing unit at the no-wait access mode. In contrast, when the address data indicates the OSD-RAM, a value "1" is output from the OR gate to the BIU, an access mode of the CPU is set to a 1-wait access mode corresponding to a double cycle, and the CPU accesses the OSD-RAM in the first half of the double cycle. When the accessing of the OSD logical circuit to the OSD-RAM is performed simultaneously with the accessing of the CPU to the OSD-RAM, the OSD logical circuit accesses the OSD-RAM in the second half of the double cycle. Therefore, software processing efficiency can be improved.
|
