| 摘要 |
A method of disabling active termination on an SCSI device when the SCSI device is not at the terminal end of the SCSI bus chain, and circuitry for accomplishing that method. An SCSI device has selectable active termination. When the SCSI device is off, the active termination circuitry is powered by the termination power line of the SCSI bus, and so the termination circuitry does not require power to the SCSI device to work properly. The SCSI device has two ports for connection in the SCSI chain, and the SCSI device detects whether a device is present on each of those ports by detecting whether a line that pulled to ground has in fact been pulled to ground. If both ports are connected to SCSI device, then the SCSI device disables its active termination using the disconnect input of the circuit it uses for active termination of the SCSI bus. Further, the SCSI device can communicate whether devices are connected to each of its SCSI ports to a host computer system via the system bus. |
