LVD input characteristics

Each differential signal received by LVD interface receiver circuits shall have the following input characteristics when measured at the disc drive connector:

Steady state Low level input differential voltage = 0.030 V = < Vin = < 3.6 V (signal negation/logic 0) Steady state High level input differential voltage = –3.6 V = < Vin = < –0.030 V (signal assertion/logic 1) Differential voltage = +0.030 V minimum with common-mode voltage range 0.845 V = < Vcm = < 1.655 V. (T10/1302D revision 14, section A.3.2).

 

VCCA

 

VCCB

Single

LVD Signal Drivers

Single

Single

 

Ended

 

Ended

Ended

Circuitry

 

Receiver

Negation

 

LVD

 

Driver

 

 

 

 

Receiver

 

 

Single

 

 

Single

Ended

 

 

Ended

Ground

 

 

Assertion

Driver

 

 

Driver

 

LVD Signal Drivers

 

 

Ground

 

 

 

Single Ended:

GND

—Signal

LVD:

+Signal

—Signal

Figure 27. Typical SE-LVD alternative transmitter receiver circuits

9.7.1.1General cable characteristics

To minimize discontinuities and signal reflections, cables of different impedances should not be used in the same bus. Implementations may require trade-offs in shielding effectiveness, cable length, the number of loads, transfer rates, and cost to achieve satisfactory system operation. If shielded and unshielded cables are mixed within the same SCSI bus, the effect of impedance mismatch must be carefully considered. Proper impedance matching is especially important in order to maintain adequate margin at fast SCSI transfer rates.

9.7.1.2Single-ended drivers/receivers

The maximum total cable length allowed with drives using single-ended I/O driver and receiver circuits depends on several factors. Table 18 lists the maximum lengths allowed for different configurations of drive usage. These values are from the SPI documents. All device I/O lines must have equal to or less than 25 pf capacitance to ground, measured at the beginning of the stub.

Table 18: Cable characteristics for single-ended circuits

 

 

maximum length

Transmission line impedance

 

Maximum number of

between SCSI S.E.

 

 

 

 

 

I/O transfer rate

devices on the bus

terminators

REQ/ACK

Other signals

 

 

 

 

 

<10M transfers/s (Fast 10)

16 (wide SCSI bus)

3 meters (9.8 ft)

90 + 6 Ohms

90 + 10 Ohms

 

 

 

 

 

<20M transfers/s (Fast 20)

4 (wide SCSI bus)

3 meters (9.8 ft)

90 + 6 Ohms

90 + 10 Ohms

 

 

 

 

 

<20M transfers/s (Fast 20)

8 (wide SCSI bus)

1.5 meters (4.9 ft)

90 + 6 Ohms

90 + 10 Ohms

 

 

 

 

 

A stub length of no more than 0.1 meter (0.33 ft) is allowed off the mainline interconnection with any connected equipment. The stub length is measured from the transceiver to the connection to the mainline SCSI bus.

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

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Seagate ST3300007LW/LC manual LVD input characteristics, General cable characteristics, Single-ended drivers/receivers

ST3300007LW/LC, ST373207LW/LC, ST3146707LW/LC specifications

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