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60
+5V
5.6K
Transmit/Receive
Enable
[1]
DIFFSENS [6]
Transmit or
Receive
R
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 9.6.3.2 from first SCSI device at
beginning to end of daisy chain. See Section 9.7.2 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 ("N," "W," and "WD" models) for powering
external terminators if the drive option select header jumper TP (Figures 8 and 9a) is installed in rightmost
position "TP." See pin assignment Table 14 for pins assigned to terminator power.
[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 14.
Figure 18.
Typical differential I/O line transmitter/receiver and terminators
+5V
TE
LSI
XCVR
RE
Disable
1
1
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
R
2
Elite 23 Product Manual, Rev. A
[3]
Twisted or Flat
Cable Pair
Term
[5]
Power
330
Ohm
1
150
Ohm
1
330
Ohm
[7]
[4]
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