Seagate ST12400N Product Manual page 71

Product Manual - Hawk 2 Family SCSI-2 (Volume 1), Rev. B
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+5V
5.6K
Transmit/Receive
Enable (1)
DIFFSENS (6)
Transmit or
Receive
Signal (2)
SCSI Device at Beginning of I/O Cable
(usually Host Adaptor/Initiator)
Notes.
[1] Positive Logic Enables Transmitter (+5 V = Asserted)
Negative Logic Enables Receivers (0 V = Asserted)
[2] Negative Logic Signal (0 V = Asserted)
[3] Total interface cable length should not exceed value given in paragraph 11.6.2.2 from first SCSI device at
beginning to end of daisy-chain. See section 11.6.4.2 for signal characteristics.
[4] I/O Line terminators. If SCSI device is a Seagate disc drive, terminators and a place to plug them in must
be provided external to the drive by user, systems integrator or host equipment manufacturer where needed.
The drive has no terminators and there are no provisions on the drive for terminator installation.
[5] Arrangements for connecting terminator power to the terminators must be made by the systems designer.
As a help, drive +5 V power is made available on SCSI bus pin 26 for powering external terminators if the
drive option select header jumper TP (Figure 10.1-1) is installed in rightmost position "TP".
[6] SCSI I/O line (pin 21) disables I/O circuits if single-ended cable plugged in or cable plugged in upside
down.
[7] SCSI I/O cable ground. See Table 11.6.3-1b.
Figure 11.6.4-2. Typical differential I/O line transmitter/receiver and external terminators
+5V
TE
LSI
XCVR
RE
Disable
1
1
R 2
+5V
Transmit/Receive
Enable
DIFFSENS (6)
Transmit or
Receive
Signal (2)
SCSI Device at End of I/O Cable
(Drive/Target)
Term
(5)
Power
330
(4)
Ohm
150
Ohm
330
Ohm
(7)
+5V
5.6K
TE
LSI
XCVR
(1)
RE
Disable
1
1
R 2
Twisted or Flat
(3)
Cable Pair
Term
(5)
Power
330
(4)
Ohm
150
Ohm
330
Ohm
(7)
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