Seagate ST12450W, Product Manual

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ST12450W/WD Product Manual, Rev. A 55
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.
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 Receiver input
Negated (0)
≥
2.5V :
≤
5.25V
≥
2.0V : < 5.25V
Asserted (1)
≤
0.4V :
≥
0.0V
≤
0.8V : > 0.0V
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.
Transmitter
(or transceiver)
Line Driver
Flat
Cable
Pair
[3]
[2]
[4]
[1]
+2.85V
110
Ohm
[4]
[1]
+2.85V
110
Ohm
Receiver
Line Receiver
[2]