Patent
1994-08-31
1996-10-15
Lee, Thomas C.
395856, 395842, 395281, G06F 1300
Patent
active
055663451
ABSTRACT:
In a data processing system having a data processor coupled to a SCSI channel disposed for transmitting and receiving data between the data processor and a peripheral storage subsystem, a bridge controller for expanding the maximum allowable number of disk drives connectable to the SCSI channel. The bridge controller comprises a microprocessor having input/output terminals coupled to a CPU bus; a memory having input/output terminals coupled to a DMA bus; a buffer coupled between the CPU bus and the DMA bus; a first transceiver coupled between the DMA bus and the SCSI channel; a second transceiver coupled between the DMA bus and the disk drives; and, a circuit for controlling the direction of data flow through the buffer. The circuit has input/output terminals coupled to the CPU bus and a control output coupled to a direction control input terminal of the buffer. The circuit also includes a decoder for decoding the operation requested by the microprocessor and for granting a DMA bus request signal in response thereto; and, an arbitrator that arbitrates between DMA request signals from the microprocessor, the first transceiver or the second transceiver so that a DMA bus grant signal is granted to only one at a time.
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Chen Duo
Lee Thomas C.
Petersen Steven R.
Richebourg J. Ronald
Starr Mark T.
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