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ST12450W/WD Product Manual, Rev. A
Input characteristics
Each signal received by differential interface drives should have the following
input characteristics when measured at the disc drive 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 19. 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] You must provide terminators.
+5V
DE
LSI
XCVR
RE
1
1
R
2
57
[3]
[4]
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