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68
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 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 conform to EIA RS-485-1983.
+5V
5.6K
Transmit/Receive
Enable
[1]
Transmit or
Receive
Signal
[2]
Figure 26. Typical differential I/O line transmitters/receivers
and terminators
Notes:
[1] Positive logic enables transmitters ( 5V = asserted).
Negative logic enables receivers (0V = asserted).
[2] Negative logic signal (0V = asserted).
[3] Total interface cable length should not exceed 82.1 feet (25 meters) from
the host to the end of the daisy chain.
[4] You must provide terminators.
Barracuda 1 and 2 Product Manual, Rev. C
+5V
DE
LSI
XCVR
RE
1
1
R
2
[3]
[4]
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