Cable Select Option; Figure 4. Connecting Cable-Selected Drives - Seagate ST3780A Product Manual

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2.5 Cable select option

If your computer and both of your drives support cable select, you can
use the cable select option to determine the master and slave. To
configure your drives using cable select, you need to install jumpers and
use a special cable-select cable as follows:
• Install jumpers on pins 1 and 2 and pins 3 and 4 of the master/slave
jumper block J5 and on pins 6 and 8 of the options jumper block J8.
These jumper blocks are shown in Figure 3 on page 18.
• You must use an interface ribbon cable built to support master and
slave selection. The cable and its connectors must connect the CSEL
signal line to pin 28 of the master drive, but not to the slave drive (see
Figure 4). That is, the drive that is plugged into the I/O connector
connecting the CSEL signal line to pin 28 is the master. The drive
plugged into the I/O connector, whose pin 28 is open, is the slave. Pin
28 of its cable connector is not connected to the CSEL line.
CSEL not carried
to pin 28 of
this connector
Pin 28 grounded
at computer
Computer

Figure 4. Connecting cable-selected drives

Medalist Family AT Product Manual, Rev. A
Slave
Master