11.4.6 Sas Transmitters And Receivers; 11.4.7 Power; Signal Characteristics; 11.5.1 Ready Led Out - Seagate ST900MM0006 Product Manual

11.4.6 SAS transmitters and receivers

A typical SAS differential copper transmitter and receiver pair is shown in Figure 22. The receiver is AC coupling to eliminate
ground shift noise.
Figure 22. SAS transmitters and receivers

11.4.7 Power

The drive receives power (+5 volts and +12 volts) through the SAS device connector.
Three +12 volt pins provide power to the drive, 2 short and 1 long. The current return for the +12 volt power supply is through
the common ground pins. The supply current and return current must be distributed as evenly as possible among the pins.
Three +5 volt pins provide power to the drive, 2 short and 1 long. The current return for the +5 volt power supply is through
the common ground pins. The supply current and return current must be distributed as evenly as possible among the pins.
Current to the drive through the long power pins may be limited by the system to reduce inrush current to the drive during hot
plugging.
11.5 S
IGNAL CHARACTERISTICS
This section describes the electrical signal characteristics of the drive's input and output signals. See Table 16 for signal type
and signal name information.

11.5.1 Ready LED Out

The Ready LED Out signal is driven by the drive as indicated in Table 17.
Table 17 Ready LED Out conditions
N
ORMAL COMMAND ACTIVITY
Ready LED Meaning bit mode page 19h
Spun down and no activity
Spun down and activity (command executing)
Spun up and no activity
Spun up and activity (command executing)
Spinning up or down
Format in progress, each cylinder change
The Ready LED Out signal is designed to pull down the cathode of an LED. The anode is attached to the proper +3.3 volt
supply through an appropriate current limiting resistor. The LED and the current limiting resistor are external to the drive. See
Table 18 for the output characteristics of the LED drive signals.
S 10K.6 SAS P
AVVIO RODUCT
(50% on and 50% off, 0.5 seconds on and off for 0.5 seconds)
M , R . C
ANUAL EV
LED
STATUS
0
Off
On
On
Off
Blinks steadily
Toggles on/off
1
Off
On
Off
On
62