| 摘要 |
Disposed in a single integrated circuit chip are a central processing unit (CPU) for performing instruction execution, an on-screen display (OSD) circuit for displaying character information on a display screen, a read only memory (ROM) which is arbitrarily divided into a first ROM storage space for use by the CPU and a second ROM storage space for use by the OSD circuit, a random access memory (RAM) which is arbitrarily divided into a first RAM storage space for use by the CPU and a second RAM storage space for use by the OSD circuit, and a common bus which is composed of a data bus and an address bus. The CPU, the OSD circuit, the ROM, and the RAM are connected to the common bus in such a way as to allow the CPU and the OSD circuit to acquire an exclusive right to use the ROM and the RAM. When the common bus is not in use by the CPU, a message that said common bus is made available to the OSD circuit is communicated from the CPU to the OSD circuit via a bus liberation signal line, and the OSD circuit obtains a right to use the common bus.
|
