Seagate ST100FM0002 ユーザーズマニュアル
P
ULSAR
.2 SAS P
RODUCT
M
ANUAL
, R
EV
. C
57
11.4.6
SAS transmitters and receivers
A typical SAS differential copper transmitter and receiver pair is shown in Figure 20. The receiver is AC coupling to eliminate ground shift
noise.
noise.
Figure 20.
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.
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.
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 24 for signal type and signal
name information.
name information.
11.5.1
Ready LED Out
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 26 for the output
characteristics of the LED drive signals.
an appropriate current limiting resistor. The LED and the current limiting resistor are external to the drive. See Table 26 for the output
characteristics of the LED drive signals.
Table 25 Ready LED Out conditions
N
ORMAL COMMAND ACTIVITY
LED
STATUS
Ready LED Meaning bit mode page 19h
0
1
Drive stopped, not ready, and no activity
Off
Off
Drive stopped, not ready, and activity
(command executing)
On
On
Drive started, ready, and no activity
On
Off
Drive started, ready, and activity
(command executing)
Off
On
Drive transitioning from not-ready state to
ready state or the reverse.
Blinks steadily
(50% on and 50% off, 0.5 seconds on and off for 0.5 seconds)
FORMAT UNIT in progress,
Toggles on/off
Table 26 LED drive signal
S
TATE
T
EST CONDITION
O
UTPUT VOLTAGE
LED off, high
0 V
≤
VOH
≤
3.6 V
-100 μA < I
OH
< 100 μA
LED o
n, low
I
OL
= 15 mA
0
≤
V
OL
≤
0.225 V