Product manual

Barracuda 2LP Product Manual, Rev. D 55
10.2 Synchronized spindles interface
The synchronized spindles interface (SSI) allows several drives operating
from the same host to operate their spindles at a synchronized rotational
rate. Details of the electrical and physical interfaces follow in Section 10.2.1.
The system operation is described in Section 5.7.
10.2.1 Electrical description
The electrical interface consists of one digital TTL reference index signal
and ground. The reference index signal (SSREF+) is an output if the drive
is configured as a master and is an input otherwise. The reference index
signal is connected from drive to drive in a daisy-chain fashion as shown in
Figure 4.
10.2.1.1 Drivers and receivers
Figure 22 shows a diagram of the driver/receiver circuit. The driver circuits
have the following electrical specifications:
Negated (false): 0.V to +0.4V @ I = –24 mA (max)
Asserted (true): +2.24V to +5.25V @ I = +250 µA
 Driver Receiver
2.21K Ohm
SSREF +
GND
Main PWA
J4 pin 6 on N/ND/WC/DC drives
J5 pin 11 on W/WD drives
+5V
J4 pin 5 on N/ND drives
J5 pin 12 on W/WD drives
J4 pin 10 on WC/DC drives
Open
Collector
Figure 22. SCSI reference index signal driver/receiver combination