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62
_____________________________________________________________________________________
+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 Section 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. See section 11.6.4.3. 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 de-
signer. As a help, drive +5 V power is made available on SCSI bus (see pinouts on Tables 11.6.3-1a, b,
c, d) 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 16 on 68 pin I/O; pin 46 on 80 pin I/O) disables I/O circuits if single-ended cable
plugged in or cable plugged in upside down.
[7]
SCSI I/O cable ground. See Tables 11.6.3-1b and 11.6.3-1d.
Figure 11.6.4-2. Typical differential I/O line transmitter/receiver and external terminators
Product Manual - Hawk 4 Family (Wide) SCSI-2 (Volume 1), Rev. E
+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
(1)
XCVR
RE
Disable
1
1
R
2
(3)
Twisted or Flat
Cable Pair
Term
(5)
Power
330
(4)
Ohm
150
Ohm
330
Ohm
(7)
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