PURPOSE: To scale down the overall constitution by installing a through bus directly connecting a port that a microprocessor accesses and a port transferring data through a bus LSI in the interior of a disk controller and preparing a means deciding whether the bus is made effective or not.
CONSTITUTION: If an FF42 is set to a logic '0', a normal data transfer can exchange data between a disk and the bus LSI30, because a switching circuit 41 connects the port 12 and the bus LSI30. When the microprocessor 20 controls the bus LSI30, first the FF42 is set to a logic '1'. Then the switching circuit 41 connects the ports 11 and 12, which means that the data bus of the microprocessor 20 is directly connected to the data bus of the bus LSI30. Afterward, the microprocessor 20 outputs an address to designate the bus LSI30, it can directly access the bus LSI30. Since at that time the chip select signal of an HDC10 is not outputted, the HDC10 is never affected which value lines in the port 11.
IZEKI TOSHIYUKI
KAWAMURA TETSUSHI
MEGA MASAYUKI
Next Patent: INPUT DEVICE FOR DISPLAY POSITION INFORMATION