Barracuda 18LP Installation Guide, Rev. B
23
This drive must not be operated with that kind of control-
ler. This drive can operate with older SE controllers, how-
ever.
• “LW” and “LC” models use SCSI multimode I/O circuits. Multi-
mode circuits operate either in single-ended mode or low volt-
age differential mode. No high voltage differential devices
should be connected in the I/O daisy chain with “LW” or “LC”
model drives. The state of the I/O “DIFFSNS” line determines
whether the devices on the SCSI bus operate their I/O circuits
in single-ended or low voltage differential mode. The host
device on the SCSI bus operates the “DIFFSNS” line. How-
ever, the SE jumper on J2 forces “DIFFSNS” to nominal
ground (see Figure 12). The host device cannot override the
SE jumper. If “DIFFSNS” is at nominal ground (0V to .6V), all
of the bus receivers/drivers operate in single-ended mode. If
“DIFFSNS” is between .7V and 1.9V, all bus receiver/drivers
operate in low voltage differential (LVD) mode.
• “LC” and “LW” models have a “wide” (16-bit) SCSI data bus
rather than the standard (non-wide) 8-bit SCSI data bus; how-
ever, you can use these wide drives on a standard (non-wide)
8-bit data bus. However, the unused lines must be terminated
the same as the used lines.
Figures 3a, 3b, and 3c show typical drive connections. The fol-
lowing tables list the maximum cable lengths and number of
devices allowed on a daisy-chain cable for I/O data transfer rates
shown.
Note. For LVD operation, twisted pair cables are recom-
mended. For LVD Fast-40 operation, twisted pair cables
are
strongly
recommended. For Fast-80 operation,
twisted pair cables are
required
.
