Product manual

72 Barracuda 2LP Product Manual, Rev. D
ST31250W/WD and ST32550W/WD drives
Recommended mating wide cable connector part numbers:
AMP 786096-7, female 68-pin
AMP 1-480420-0, power connector 4 circuit housing
BERG 69307-012 (12-position, 2 x 6, 2 mm receptacle housing)
ST31250WC/DC and ST32550WC/DC drives
No cable is required. Recommended mating SCA part numbers:
AMP Vertical (SCA sequence), 80-position
787320-1 with polarization feature
787320-2 without polarization feature
AMP Vertical (Mating blind mate SCA-2), Rcpt Assembly, 80-position
787311-1 3.18 mm tail length, with polarization feature
787331-2 3.18 mm tail length, without polarization feature
787311-3 4.57 mm tail length, with polarization feature
787331-4 4.57 mm tail length, without polarization feature
11.7.3 Electrical description
ST31250N, ST31250W, ST32550N, and ST32550W drives use single-
ended interface signals. These signals must be terminated with 110 ohm
active terminator circuits at each end of the total cable. Single-ended circuits
use open collector or three-state drivers. ST31250N, ST31250W, ST32550N
and ST32550W drives can be configured to provide the SCSI termination.
ST31250ND, ST31250WD, ST32550ND and ST32550WD drives use differ-
ential interface signals. Each of these signals must be terminated at each end
of the total cable with 330 ohms to +5V and 330 ohms to ground with 150
ohms between each differential pair. All I/O circuits are open collector, three-
state drivers. Differential I/O drives are shipped without terminators and have
no provisions for adding terminator sockets on the PCB. You must provide
external termination for these drives.
ST31250WC/DC and ST32550WC/DC drives use the single-connection
attachment (SCA connector). This 80-pin connector plugs directly into a
back panel or plane; no external cables are required. Active terminators on
the back panel must be provided. This connector is not recommended if
cabling is required.
11.7.3.1 Single-ended drivers/receivers
Note. All single-ended terminators must be ANSI SCSI-2 alternative 2
active terminators.
Typical single-ended driver and receiver circuits for the Barracuda 2LP
family are shown in Figure 28. Use terminator circuits only when the disc
drive is first or last on the daisy chain. (See Note 1 following Figure 29.)
Transmitter characteristics
Single-ended drives use an ANSI SCSI compatible open-collector single-
ended driver. This driver is capable of sinking a current of 48 mA with a low-
level output voltage of 0.4V.