Automatic disabling of SCSI bus terminators
First Claim
1. A method for automatically enabling and disabling a SCSI termination device on a SCSI bus requiring termination at both ends of the SCSI bus, the SCSI bus having a first and a second data width portion, the SCSI bus receiving SCSI devices of first and second data widths, the second data width portion being greater than the first data width portion and including the first data width portion, the method comprising the steps of:
- providing a first SCSI termination device placed near a first bus port which carries the second data width portion for selectively terminating the first data width portion of the SCSI bus;
providing a second SCSI termination device connected near said first bus port for selectively terminating the second data width portion of the SCSI bus other than the first data width portion;
detecting if a first data width SCSI device is connected to said first bus port;
detecting if a second data width SCSI device is connected to said first bus port;
disabling said first and second SCSI termination devices if a second data width SCSI device is detected;
disabling said first SCSI termination device and enabling said second SCSI termination device if a first data width device is detected; and
enabling said first and second SCSI termination devices if neither a first or second data width SCSI device is detected.
3 Assignments
0 Petitions
Accused Products
Abstract
A system for detecting the presence and size of a SCSI device on a SCSI bus and terminating the SCSI bus accordingly. A SCSI controller is capable of driving two branches of a SCSI bus, each branch having a different data size. When the SCSI controller is at the end of a SCSI chain, termination is enabled, otherwise termination is disabled. Termination is performed on the portions of the SCSI data bus requiring termination based on the presence and size of SCSI devices on the branches used.
50 Citations
19 Claims
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1. A method for automatically enabling and disabling a SCSI termination device on a SCSI bus requiring termination at both ends of the SCSI bus, the SCSI bus having a first and a second data width portion, the SCSI bus receiving SCSI devices of first and second data widths, the second data width portion being greater than the first data width portion and including the first data width portion, the method comprising the steps of:
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providing a first SCSI termination device placed near a first bus port which carries the second data width portion for selectively terminating the first data width portion of the SCSI bus; providing a second SCSI termination device connected near said first bus port for selectively terminating the second data width portion of the SCSI bus other than the first data width portion; detecting if a first data width SCSI device is connected to said first bus port; detecting if a second data width SCSI device is connected to said first bus port; disabling said first and second SCSI termination devices if a second data width SCSI device is detected; disabling said first SCSI termination device and enabling said second SCSI termination device if a first data width device is detected; and enabling said first and second SCSI termination devices if neither a first or second data width SCSI device is detected. - View Dependent Claims (2, 3, 4, 5)
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6. A computer system, comprising:
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a bus; a processor coupled to said bus; a SCSI bus coupled to said bus, said SCSI bus requiring termination at both ends of the SCSI bus, said SCSI bus having a first and a second data width portion, said SCSI bus for receiving SCSI devices of first and second data widths, the second data width being greater than the first data width and including the first data width; a SCSI device coupled to said SCSI bus; a first bus port which carries the second data width portion; a first SCSI termination device connected near said first bus port for selectively terminating the first) data width portion of the SCSI bus; a second SCSI termination device placed near said first bus port for selectively terminating the second data width portion of the SCSI bus other than the first data width portion; and a termination control circuit coupled to said first SCSI termination device to said second SCSI termination device, and to said first bus port, said termination control circuit being adapted to detect if a first data width SCSI device is connected to said first bus port and if a second data width SCSI device is connected to said first bus port, wherein said termination control circuit disables said first and second SCSI termination devices if a second data width SCSI device is detected, wherein said termination control circuit disables said first SCSI termination device and enables said second SCSI termination device if a first data width device is detected, and wherein said termination control circuit enables said first and second SCSI termination devices if neither a first or second data width SCSI device is detected. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13)
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14. An apparatus for automatically terminating a SCSI bus requiting termination at both ends of the SCSI bus in a computer system, the SCSI bus having a first and a second data width portion, the SCSI bus receiving SCSI devices of first and second data widths, the second data width being greater than the first data width and including the first data width, the apparatus comprising:
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a first bus port which carries the second data width portion; a first SCSI termination device placed near said first bus port for selectively terminating the first data width portion of the SCSI bus; a second SCSI termination device placed near said first bus port for selectively terminating the second data width portion of the SCSI bus other than the first data width portion; and a termination control circuit coupled to said first SCSI termination device, to said second SCSI termination device, and to said first bus port, said termination control circuit being adapted to detect if a first data width SCSI device is connected to said first bus port and if a second data width SCSI device is connected to said first bus port, wherein said termination control circuit disables said first and second SCSI termination devices if a second data width SCSI device is detected, wherein said termination control circuit disables said first SCSI termination device and enables said second SCSI termination device if a first data width device is detected, and wherein said termination control circuit enables said first and second SCSI termination devices if neither a first or second data width SCSI device is detected. - View Dependent Claims (15, 16, 17, 18, 19)
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Specification