Apparatus and method for achieving improved SCSI bus control capacity

Claim 1

A method for transferring data across a SCSI bus to which first, second, and third devices are attached and are addressed logically by associating a SCSI but data bit with a predetermined physical device address assigned to each of the devices, comprising the steps of: setting the first and second devices to a common first logical device address; setting the third device to a second logical device address; addressing the second device by asserting from the first device the first logical device address on the SCSI bus; establishing a connection between the first and second devices; transferring data across the SCSI bus between the first and second devices, the data comprising a command issued by the first device and a response from the second device to the command, the command and the response being completed prior to establishing a connection between the first device and the third device; detecting in the second device one of a reselection signal asserted by the third device and a simultaneous presence of more than one logical device address asserted on the SCSI bus; and inhibiting the second device from responding to subsequent data transferred from the third device to the first device.

Claim 2

A method for transferring data across a SCSI bus to which first, second, and third devices are attached and are addressed logically by associating a SCSI but data bit with a predetermined physical device address assigned to each of the devices, comprising the steps of: setting the first and second devices to a common first logical device address; setting the third device to a second logical device address; addressing the second device by asserting from the first device the first logical device address on the SCSI bus; establishing a connection between the first and second devices; transferring data across the SCSI bus between the first and second devices, the data comprising a command issued by the first device and a response from the second device to the command, the command and the response being completed prior to establishing a connection between the first device and the third device; detecting in the second device one of a reselection signal asserted by the third device and a simultaneous presence of more than one logical device address asserted on the SCSI bus; and inhibiting the second device from responding to subsequent data transferred from the third device to the first device.

Claim 5

A method for transferring data across a SCSI-I bus to which more than eight devices are attached and are addressed logically by associating a SCSI-I bus data bit with a predetermined physical device address assigned to each of the devices, and in which the SCSI-I bus communicates with a first computer system with which a first device is associated and a second computer system with which a third device is associated, comprising the steps of: installing nine devices in the SCSI-I bus, the devices including at least the first device through the ninth device; setting the first device to a first logical device address; setting the third device through ninth device to a respective second logical device address through an eighth logical device address; setting the second device to the first and second logical device addresses; addressing the second device by asserting from the first device the first logical device address on the SCSI-I bus; establishing a connection between the first and second devices; transferring data across the SCSI-I bus between the first and second devices, the data comprising a command issued by the first device and a response from the second device to the command, the command and the response being completed prior to establishing a connection between the first device and any of the third through ninth devices; establishing a connection between the second device and either one of the first or third devices; detecting in the second device one of a reselection signal and a simultaneous presence of more than one logical device address asserted on the SCSI bus; and inhibiting the second device from responding to subsequent data transferred from the third device to the first device.

Claim 6

A method for transferring data across a SCSI-I bus to which more than eight devices are attached and are addressed logically by associating a SCSI-I bus data bit with a predetermined physical device address assigned to each of the devices, and in which the SCSI-I bus communicates with a first computer system with which a first device is associated and a second computer system with which a third device is associated, comprising the steps of: installing nine devices in the SCSI-I bus, the devices including at least the first device through the ninth device; setting the first device to a first logical device address; setting the third device through ninth device to a respective second logical device address through an eighth logical device address; setting the second device to the first and second logical device addresses; addressing the second device by asserting from the first device the first logical device address on the SCSI-I bus; establishing a connection between the first and second devices; transferring data across the SCSI-I bus between the first and second devices, the data comprising a command issued by the first device and a response from the second device to the command, the command and the response being completed prior to establishing a connection between the first device and any of the third through ninth devices; establishing a connection between the second device and either one of the first or third devices; detecting in the second device one of a reselection signal and a simultaneous presence of more than one logical device address asserted on the SCSI bus; and inhibiting the second device from responding to subsequent data transferred from the third device to the first device.