Seagate Cheetah 18XL, Руководство по эксплуатации продукта

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Cheetah 18XL Product Manual, Rev. A 69
*These voltages shall be measured between the output terminal and the SCSI device’s logic ground reference.
The output characteristics shall additionally conform to EIA RS-485.
Figure 24. LVD output signals
Input characteristics
Each signal (Vs) received by LVD interface receiver circuits shall have the following input characteristics when
measured at the disk drive connector:
Steady state Low level output voltage* = 0.030 V = < V
s
= < 3.6 V (signal negation/logic 0)
Steady state High level output voltage* = –3.6 V = < V
s
= < –0.030 V (signal assertion/logic 1)
Differential voltage = +0.30 V minimum with common-mode voltage ranges 0.700 V = < V
cm
= < 1.800 V.
(X3T10/1302D)
*These voltages shall be measured between the output terminal and the SCSI device’s logic ground reference.
Input characteristics shall additionally conform to EIA RS-485-983.
Figure 25. Typical SE-LVD alternative transmitter receiver circuits
9.7.1.1 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 17 lists the maximum lengths allowed for different configurations of drive
usage. These values are from the SPI-3 document. All device I/O lines must have equal to or less than 25 pf
capacitance to ground, measured at the beginning of the stub.
V1
–SIGNAL
100
Ω
V2
+SIGNAL
MEASURED
PARAMETER
STEADY STATE
LOGIC INPUT
(1 OR 0)
DEVICE CONNECTOR
100
Ω
75
Ω
Vs
D
VCCA VCCB
Single
Ended
Circuitry Single
Ended
Receiver Single
Ended
Negation
Driver
Single
Ended
Assertion
Driver
Single
Ended
Ground
Driver
Single Ended:
LVD:
LVD Signal Drivers
LVD Signal Drivers
LVD
Receiver
Ground
GND
+Signal
–Signal
–Signal