Through the SCB Device Inquiry command, the system determines which SCSI devices are attached to the adapter, and specific information about those devices. When the Device Inquiry data block has been transferred, the adapter interrupts the system. Because the length of the returned data block is device-dependent, the system should specify the amount of data to be returned. If this is not known, then the system should specify the maximum value (255) and set the suppress short exception (SS) bit to 1. After the Device Inquiry data block is transferred to the specific address, the adapter interrupts the system to indicate that the command is complete.
If a SCSI device is not attached at the assigned physical SCSI address, the command-completed-with-failure interrupt will be returned in the Interrupt Status register. The Command Complete status will indicate selection time-out. If the SCSI logical unit number is not supported by an attached SCSI physical unit, the device type in the Device Inquiry data block is set to hex 7F by the SCSI physical device.
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15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Remarks 0 0 0 1 1 1 0 0 ND NS 0 0 1 0 1 1 Device Inquiry 1 ES RE 0 0 SS 1 0 0 0 0 0 0 0 0 CH Enable Word <---------- Reserved ------------------------> <---------- Reserved ------------------------> <---------- Least Significant Word ----------> System Buffer <---------- Most Significant Word -----------> Address <---------- Least Significant Word ----------> System Buffer <---------- Most Significant Word -----------> Byte Count <---------- Least Significant Word ----------> Termination Status Block <---------- Most Significant Word -----------> Address <---------- Least Significant Word ----------> Optional SCB Chain <---------- Most Significant Word -----------> Address <---------- Reserved ------------------------> <---------- Reserved ------------------------>
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