Seagate ST800FM0012 Pulsar.2 SAS Product Manual - Page 75

Seagate ST800FM0012 Manual

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12.4.6 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. Figure 20. SAS transmitters and receivers 12.4.7 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. 12.5 Signal 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. 12.5.1 Ready LED Out The Ready LED Out signal is driven by the drive as indicated in Table 25. Table 25: Ready LED Out conditions LED status 0 Off On On Off 1 Off On Off On Normal command activity Ready LED Meaning bit mode page 19h Drive stopped, not ready, and no activity Drive stopped, not ready, and activity (command executing) Drive started, ready, and no activity Drive started, ready, and activity (command executing) Drive transitioning from not-ready state to ready state or the reverse. FORMAT UNIT in progress, Blinks steadily (50% on and 50% off, 0.5 seconds on and off for 0.5 seconds) Toggles on/off Pulsar.2 SAS Product Manual, Rev. B 67

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Pulsar.2 SAS Product Manual, Rev. B
67
12.4.6
SAS transmitters and receivers
A typical SAS differential copper transmitter and receiver pair is shown in Figure 20. The receiver is AC cou-
pling to eliminate ground shift noise.
Figure 20.
SAS transmitters and receivers
12.4.7
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 sup-
ply 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.
12.5
Signal 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.
12.5.1
Ready LED Out
The Ready LED Out signal is driven by the drive as indicated in Table 25.
Table 25:
Ready LED Out conditions
Normal 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