Seagate Elite 23 ST423451N, Product Manual

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58 Elite 23 Product Manual, Rev. A
9.7 Electrical description
ST423451N and ST423451W models use single-ended interface signals. These signals must be terminated
with 110-ohm active termination circuits at each end of the total cable. Single-ended circuits use open collector
or three state drivers. All of these models can be configured to provide the SCSI termination.
ST423451WD models use differential interface signals and each of these must be terminated at each end of
the total cable with 330 ohms to +5 V and 330 ohms to ground with 150 ohms between each differential pair. All
I/O circuits are open collector, three state drivers. Differential I/O drives are shipped without terminators. These
drives have no provisions for adding terminator sockets on the PCB. This means some method of external ter-
mination must be provided by the user when termination is required.
9.7.1 Single-ended drivers/receivers
Typical single-ended driver and receiver circuits are shown in Figure 17. Use terminator circuits only where the
disc drive is first or last in the daisy chain. See Note 1 following Figure 17.
Transmitter characteristics
Single-ended drives use an ANSI SCSI compatible open collector single-ended driver. This driver is capable of
sinking a current of 48 mA with a low level output voltage of 0.4 volt.
Receiver characteristics
Single-ended drives use an ANSI SCSI single-ended receiver with hysteresis gate or equivalent as a line
receiver.
Figure 17. Single-ended transmitters and receivers
Notes.
[1] Part of active terminator circuits. Non-removable LSI terminators, enabled in the drive (“N” and “W” mod-
els only) with jumper plug TE when it is the first or last in the daisy chain.
[2] ANSI SCSI compatible circuits.
[3] Total interface cable length should not exceed that specified in Section 9.6.3.1.
[4] Source of drive terminator power is an active circuit which has an input source voltage selected by jumper
plug TP. See Figures 8 and 9a. Applies to “N” and “W” models only.
[5] Interface signal levels and logical sense at the drive I/O connector for “N,” “W,” and “WC” models are
defined as follows:
Vil (low-level input voltage) = 1.0 V maximum (signal true); minimum = Vss – 0.5 V.
Vih (high-level input voltage) = 1.9 V minimum (signal false); maximum = Vdd +0.5V.
Vihys (Input Hysteresis) = 425 mV minimum
Transmitter
(or transceiver)
Line Driver
Flat
Cable
Pair
[3]
[5]
[2]
[4]
[1]
110
Ohm
[4]
[1]
110
Ohm
Receiver
Line Receiver
[2]
TP TP