Sas Transmitters And Receivers; Power; Signal Characteristics; Ready Led Out - Seagate ST8000NM0065 Product Manual

11.4.6 SAS transmitters and receivers

A typical SAS differential copper transmitter and receiver pair is shown in Figure 12. The receiver is AC coupling to eliminate ground shift noise.
TX
Transmitter
100
TY
Figure 12. 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

Signal characteristics

This section describes the electrical signal characteristics of the drive's input and output signals. See Table 12 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 13.
Table 13 Ready LED Out conditions
Normal 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 14 for the output characteristics of
the LED drive signals.
Table 14 LED drive signal
State
LED off, high
LED on, low
Seagate Enterprise Capacity 3.5 HDD v5 SAS Product Manual, Rev. F
Differential
Transfer Medium
(50% on and 50% off, 0.5 seconds on and off for 0.5 seconds)
Test condition
0 V ≤ VOH ≤ 3.6 V
IOL = 15 mA
.01
RX
Receiver
100
RY
.01
LED status
0
Off
On
On
Off
Blinks steadily
Toggles on/off
Output voltage
-100 μA < IOH < 100 μA
0 ≤ VOL ≤ 0.225 V
1
Off
On
Off
On
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