Figure 18. Single-Ended Transmitters And Receivers - Seagate ST12450W Product Manual

ST12450W/WD Product Manual, Rev. A
11.7.3.1 Single-ended drivers/receivers
Typical single-ended driver and receiver circuits for the Barracuda 2, 2HP
family are shown in Figure 18. Terminator circuits shown are needed only
when the disc drive is first or last on the daisy chain. (See Note 1 following
Figure 18.)
Note. All single-ended terminators must be ANSI SCSI-2 alternative 2
active terminators.
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 0.4V.
Receiver characteristics
Single-ended drives use an ANSI SCSI single-ended receiver with hyster-
esis gate or equivalent as a line receiver.
Line Driver
Transmitter
(or transceiver)
[2]

Figure 18. Single-ended transmitters and receivers

Notes:
[1] Part of active terminator circuits. Enable drive termination when it is first
or last on the daisy chain.
Interface signal levels and logical sense at the drive I/O connector are
defined as follows:
Logic level Driver output
≥ 2.5V : ≤ 5.25V ≥ 2.0V : < 5.25V
Negated (0)
≤ 0.4V : ≥ 0.0V
Asserted (1)
The difference in the voltages between input and output signals is due to
losses in the cable.
[2] ANSI SCSI compatible circuits.
[3] Total interface cable length should not exceed that specified in Section
11.7.1.2.1.
[4] Source of drive terminator power is VR1 which has an input source
voltage selected by a jumper.
[4]
+2.85V
Flat
110
Cable
[1]
Ohm
Pair
[3]
Receiver input
≤ 0.8V : > 0.0V
Line Receiver
Receiver
[4]
+2.85V
110
[1]
Ohm
[2]
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