Terminator Requirements; Figure 16. Typical Se-Lvd Alternative Transmitter Receiver Circuits - Seagate ST39173N Product Manual

72
Input characteristics
Each signal (Vs) received by LVD interface receiver circuits shall have the following input characteristics when
measuared at the disk drive connector:
Steady state Low level output voltage* = 0.030 V = < V
Steady state High level output voltage* = –3.6 V = < V
Differential voltage = +0.30 V minimum with common-mode voltage ranges 0.700 V = < V
(X3T10/1142D revision 13, p. 152)
*These voltages shall be measured between the output terminal and the SCSI device's logic ground reference.
This requirement shall be met with the input voltage varying between 0.700 V and 1.8 V, with power on or off,
and with the hysteresis equaling TBD mV, minimum.
Input characteristics shall additionally conform to EIA RS-485-983.
Figure 16. Typical SE-LVD alternative transmitter receiver circuits
9.8

Terminator requirements

Internal disc drive I/O termination (provided only in model "N" and "W" drives single ended I/O model drives)
consists of active circuits in an LSI module that is permanently mounted on the PCB. All single initiator/single
target (non-daisy-chain) applications require that the Initiator and disc drive be terminated. Daisy-chain appli-
cations require that only the units at each end of the daisy-chain be terminated. All other peripherals on the
chain must not be terminated. (See Figure 10).
Note. Remove drive terminator enabling jumper TE where terminators are not required. Removal of termina-
tor power source selection jumper TP (see Figure 7d) does not disconnect the terminator resistors
from the circuit.
It is highly recommended that ANSI SCSI-2 Standard's Alternative 2 termination (active termination) be used
for applications with single-ended ("N" and "W" models), especially if the bus will be operated at transfer rates
above 5 Mbytes/sec. The "N" and "W" models provide on-board active termination that can be disabled by
removal of the enable jumper TE (see Figure 7d).
Note. ACTIVE TERMINATORS ARE HIGHLY RECOMMENDED FOR USE IN THE DAISY-CHAIN AS
DESCRIBED ABOVE. ACTIVE AND PASSIVE TERMINATORS SHOULD NOT BE MIXED ON THE
SAME SCSI BUS.
Drive models "WD," "WC," "LW," and "LC" do not have internal terminators available. The user, systems integra-
tor or host equipment manufacturer must provide a terminator arrangement external to the drive. For "ND,"
"WD," and "LW" models, terminator modules can be purchased that plug between the SCSI I/O cable and the
drive I/O connector or on the end of a short I/O cable stub extending past the last cable connector.
VCCA
LVD Signal Drivers
Single
Ended
Circuitry
Receiver
Single
Ended
Ground
Driver
LVD Signal Drivers
Ground
Single Ended:
GND
LVD:
+Signal
Barracuda 9LP Product Manual, Rev. C
= < 3.6 V (signal negation/logic 0)
s
= < –0.030 V (signal assertion/logic 1)
s
VCCB
Single
Ended
Receiver
LVD
–Signal
–Signal
= < 1.800 V.
cm
Single
Ended
Negation
Driver
Single
Ended
Assertion
Driver