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The mating connector pins use shorter contacts to achieve power surge reductions and to aid in "hot plugging"
the drives. There are longer voltage contacts in the connector to enable the drive filter capacitors to charge.
Current to the drive through the long charge pins is limited by the system in which the drive operates. Three of
the +12 volt pins are shorter to allow capacitive pre-charging through the longer +12 volt charge pin. Two of the
+5 volt pins are shorter to allow capacitive precharging through the longer +5 volt charge pin.
9.5.7
Fault LED Out
The Fault LED Out signal is driven by the drive when:
• the drive detects failure of both ports
• the drive detects an internal failure
• the drive receives the appropriate fault LED command from the host
The Fault LED Out signal is designed to pull down the cathode of an LED. The anode is attached to the proper
+5 volt supply through an appropriate current-limiting resistor. The LED and the current-limiting resistor are
external to the drive.
9.5.8
Active LED Out
The Active LED Out signal is driven by the drive as indicated in Table 16.
Table 16:
Active LED Out conditions
Normal command activity
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 Active LED Out signal is designed to pull down the cathode of an LED. The anode is attached to the
proper +5 volt supply through an appropriate current limiting resistor. The LED and the current limiting resistor
are external to the drive.
9.5.9
– Enable Bypass Signal Port A - Port B
The – Enable Bypass Port A (– EN BYP Port A ) and – Enable Bypass Port B (– EN BYP Port B) control the
port bypass circuits (PBC) located external to the disc drive. The PBC allows a loop to remain functional in the
event of a drive failure or removal. When these signals are active, low, the PBC bypasses the drive on the
associated port. When an Enable Bypass signal is active, the corresponding Port Bypass LED signal in con-
nector J20 is driven low by the disc drive. A pull down resistor, 1K, located with the PBC on the system back
panel should be used to insure the bypass is enabled if the disc drive is not installed.
The Enable Bypass signal is active under failing conditions within the drive, on detection of the Loop Port
Bypass primitive sequence, or on removal of the drive. In the bypass state the drive continues to receive on the
inbound fibre. Enable Bypass may be deactivated by detection of a Loop Port Enable primitive sequence if the
drive has completed self-test and a hardware failure is not present.
Failure modes detected by the disc drive that will enable bypass include:
• Transmitter/receiver wrap test failure
• Loss of receive clock
• Loss of transmission clock
• Drive interface hardware error
Cheetah 4LP FC Product Manual, Rev. A
LED status
Off
On
On
Off
Blinks steadily
Toggles on/off
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