Maxtor 10K III manual Continues to monitor the Diffsens signal. If, Might occur if a

Feature Descriptions

￿￿￿￿￿￿&+((5'05The DIFFSENS signal in the SCSI bus defines the current operating mode of the SCSI bus. A level below +.5 volts defines a single-ended bus. A level between +.7 and +1.9 volts defines an LVD bus. A level above +2.4 volts defines a High Voltage Differential (HVD) bus. Before LVD was introduced, HVD was simply called Differential SCSI.

All single-ended-only devices connect the DIFFSENS signal to ground. On an LVD bus, the terminators drive the DIFFSENS signal to +1.3 volts unless some device is holding the signal at ground. HVD devices pull DIFFSENS up to +5 volts via a resistor.

The Maxtor Atlas 10K III disk drive is designed with a circuit that monitors the level of DIFFSENS at power-on. The drive then enables the appropriate circuits for LVD or single-ended operation, or disables its interface completely if it detects an HVD level on DIFFSENS.

The two normal operating environments for the Maxtor Atlas 10K III disk drive are an all-LVD or (LVD/MSE) bus, in which case it operates in its LVD mode, or a bus that contains at least one single-ended device, in which case the Maxtor Atlas 10K III disk drive operates in single-ended mode.

HVD mode is not supported by the Maxtor Atlas 10K III disk drive. Signal levels on an HVD bus can reach as high as +15 volts due to allowed common mode transients.

	device	damage may occur			mutually
		into	operating
￿￿￿￿￿￿&+((5'05After establishing￿59+6%*+0)its initial operating d			, the Maxtor Atlas 10K III disk drive
continues to monitor the DIFFSENS signal. If				cha ge in lev is d te ted, such as
might occur if a		added to or removed f om the bus, the DIFFSENS circuit
detects the change and prese ts mode change				nterrupt to the drive firmware. The
operating mode of the interface switches			the new mode 100 msec after the change
is detected, providing the new level has remain				d co stant. This delay is required to

preventCAUTION:spurioussivandThemodeLVDswitchesispluggedndHVDdue alternaivesarenoiseanon theSCSIdevicesD FFSENSHVDbusifine.anLVDexclu. -

6-10 Maxtor Atlas 10K III