Seagate ST373207LW/LC, ST3146707LW/LC manual Cables for low voltage differential drivers/receivers

Single-ended I/O cable pin assignments for LW drives are shown in Table 15.

Single-ended I/O pin assignments for LC models are shown in Table 16. The LC model does not require an I/O cable. It is designed to connect directly to a back panel connector.

9.7.1.3Cables for low voltage differential drivers/receivers

The SPI-3 and SPI-4 specification for differential impedance for LVD cables is 122.5 ± 12.5 ohms.

The maximum SCSI bus length between the terminators for a SCSI LVD point-to-point system (one initiator and one target) is 25 meters (82 feet).

The maximum SCSI bus length between the terminators for a SCSI LVD multidrop system (up to 16 total SCSI devices) is 12 meters (39.37 feet). However, implementation of this 12-meter total length is dependent on the configuration of the system and the choice of cable. See Tables 19 and 20 for examples of recommended SCSI LVD cable types and lengths.

It should be noted from the data in Tables 19 and 20 that shielded round twisted-pair cables can be used to implement a 12-meter system, while Twist-n-flat cables cannot be used to implement a 12-meter system due to higher levels of attenuation and crosstalk. In addition, twist-n-flat cables with shorter sections of twist allow greater crosstalk and their lengths must be reduced as shown in Table 20.

Table 19:	Example shielded round twisted-pair cables - into a multi-drive backplane
			Single-	Single-		Conductor
		Differential	ended	ended	Time	DC	Maximum shielded round
Cable		impedance,	impedance,	capacitance,	delay,	resistance,	twisted-pair cable length
description		nominal	nominal	maximum	nominal	nominal	for U160/U320
30 AWG		130 ohms	90 ohms	17 pF/ft	1.36 ns/ft	0.113 ohms/ft	12 meters minus the SCSI
solid							trace length of the backplane
28 AWG		123 ohms	80 ohms	19 pF/ft	1.54 ns/ft	0.067 ohms/ft	12 meters minus the SCSI
stranded							trace length of the backplane
28 AWG		132 ohms	85 ohms	20 pF/ft	1.50 ns/ft	0.065 ohms/ft	12 meters minus the SCSI
stranded							trace length of the backplane

82 Cheetah 10K.7 SCSI Product Manual, Rev. D