Product manual

Product Manual - Hawk 2 Family (Wide bus) SCSI-2 (Volume 1), Rev. A 63
_____________________________________________________________________________________
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 11.6.2.1 from first SCSI device at
beginning to end of daisychain. See section 11.6.4.1 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 systems designer 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 de-
signer. As a help, drive +5 V power is made available on model ST12400WD on SCSI bus pins 17, 18, 51
and 52 for powering external terminators if the drive option select header jumper TP (Figure 10.1-1a) is
installed in the proper position.
[6] SCSI I/O line (pin 16) disables I/O circuits if single-ended cable is plugged in.
[7] SCSI I/O cable ground. See Table 11.6.3-1b.
Figure 11.6.4-1b. Typical differential I/O line transmitter/receiver and terminators
TE
RE
LSI
XCVR
1
1
R2
+5V
+5V
5.6K
Transmit/Receive
Enable (1)
Transmit or
Receive
Signal (2)
(3)
Term
Power
(5)
330
Ohm
150
Ohm
330
Ohm
SCSI Device at Beginning of I/O Cable
(usually Host Adaptor/Initiator)
TE
RE
LSI
XCVR
1
1
R2
+5V
+5V
5.6K
Transmit/Receive
Enable (1)
Transmit or
Receive
Signal (2)
Term
Power
(5)
330
Ohm
150
Ohm
330
Ohm
SCSI Device at End of I/O Cable
(Drive/Target)
(4)
Twisted or Flat
Cable Pair
(4)
DIFFSENS (6) Disable
DIFFSENS (6)
Disable
(7)
(7)