Seagate ST3300655LW Product Manual page 77

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 = < V
Steady state High level input differential voltage = –3.6 V = < V
Differential voltage = +0.030 V minimum with common-mode voltage range 0.845 V = < V
(T10/1302D revision 20b, section A.3.1).
VCCA
LVD Signal Drivers
Single
Ended
Circuitry
Single
Ended
Ground
Driver
LVD Signal Drivers
Ground
Single Ended: GND
LVD: +Signal
Figure 18. Typical SE-LVD alternative transmitter receiver circuits
9.7.1.1 General 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.
9.7.1.2 Single-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 21 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 21: Cable characteristics for single-ended circuits
I/O transfer rate
<10M transfers/s (Fast 10)
<20M transfers/s (Fast 20)
<20M transfers/s (Fast 20)
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 15K.5 SCSI Product Manual, Rev. D
VCCB
Single
Ended
Receiver
LVD
Receiver
—Signal
—Signal
Maximum number of
devices on the bus
16 (wide SCSI bus)
4 (wide SCSI bus)
8 (wide SCSI bus)
= < 3.6 V (signal negation/logic 0)
in
= < –0.030 V (signal assertion/logic 1)
in
Single
Ended
Negation
Driver
Single
Ended
Assertion
Driver
Maximum length
between SCSI S.E.
terminators
3 meters (9.8 ft)
3 meters (9.8 ft)
1.5 meters (4.9 ft)
= < 1.685 V.
cm
Transmission line impedance
REQ/ACK Other signals
90 + 6 Ohms 90 + 10 Ohms
90 + 6 Ohms 90 + 10 Ohms
90 + 6 Ohms 90 + 10 Ohms
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