Hitachi HUS157336EL3600 - Manual (Page 19)

Drawing No. Sheet No. Revision 5
K6602906 19/46 2003/6/12
5.2 Low voltage differential (LVD) mode
The NW and NC drives have two different transceivers to allow customer to use it in
traditional systems which may use single-ended drivers and receivers, or to use it in
low voltage differential (LVD) systems which use LVD drivers and receivers.
Their I/O circuits are selectable using the I/O "DIFFSENS" line. When the I/O
"DIFFSENS" line is between -0.35V and +0.5V, the drive interface circuits operate
single-ended. When "DIFFSENS" is between +0.7V and +1.9V, the drive interface
circuits operate LVD.
Customer can configure the drive to switch between single-ended and LVD modes
using the I/O "DIFFSENS" line, or force it to operate in single-ended mode only as
described later in this document.
Note 1: To operate at LVD mode, all devices on the same bus must be running in LVD
mode. If you add any single-ended device to a bus that is operating in LVD mode,
all devices drop back to operating in single-ended mode. This eliminates the
possibility of reaching Ultra-2 SCSI transfer rates.
Note 2: Do not mix LVD drives on the same daisy chain with devices having high voltage
differential (HVD) interface circuits.