Figure 32. Typical Differential I/O Line Transmitter/Receiver And Terminators - Seagate ST15150N - Barracuda 4.3 GB Hard Drive Product Manual

ST15150N/ND/W/WD/WC/DC Product Manual, Rev. D
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.
+5V
5.6K
Transmit/Receive
Enable [1]
Transmit or
Receive
Signal [2]

Figure 32. 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).
[3] Total interface cable length should not exceed 82.1 feet (25 meters)
from the host to the end of the daisy chain.
[4] Terminators must be provided by user where needed.
+5V
DE
LSI
XCVR
RE
1
1
R 2
73
[3]
[4]