Seagate BARRACUDA 2LP, Product Manual

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74 Barracuda 2LP Product Manual, Rev. D
Output characteristics
Each signal driven by differential interface drives should have the following
output characteristics when measured at the disc drive’s SCSI connector:
Low-level output voltage*
= 2.0V maximum at low-level output current
= 55 milliamps
High-level output voltage*
= 3.0V minimum at high-level output current
= –55 milliamps
Differential voltage
= 1.0V minimum with common-mode voltage ranges
from –7V DC to
+
12V DC
* Measure these voltages between the output terminal and the SCSI
device’s logic ground reference.
The output characteristics must additionally conform to EIA RS-485-1983.
Input characteristics
Each signal received by differential interface drives should have the following
input characteristics when measured at the disc drive’s SCSI connector:
Input current on either input
=
+
2.0 milliamps maximum
(includes both receivers and passive drivers)
This requirement is met with the input voltage varying between –7V DC and
+
12V DC, with power on or off, and with the hysteresis equaling 35 mV
minimum.
The input characteristics must additionally conform to EIA RS-485-1983.
DE
RE
LSI
XCVR
1
1
R 2
+5V
+5V
5.6K
Transmit/Receive
Enable [1]
Transmit or
Receive
Signal [2]
[3]
[4]
Figure 30. Typical differential I/O line transmitter/receiver and terminators
Notes:
[1] Positive logic enables transmitter (
+
5V = asserted).
Negative logic enables receivers (0V = asserted).
[2] Negative logic signal (0V = asserted).