CHEETAH 15K.7 FC PRODUCT MANUAL, REV. E 60
11.5.8 Active LED Out
The Active LED Out signal is driven by the drive as indicated in Table 25.
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.
11.5.9 Enable port bypass signals
The – Enable Bypass Port A (– EN BYP Port A) and – Enable Bypass Port B (– EN BYP Port B) signals control the port
bypass circuits (PBC) located external to the disk 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 connector J1 is driven low by the disk drive. A pull
down resistor, 1K, located with the PBC should be used to insure the bypass is enabled if the disk 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 disk drive that will enable bypass include:
• Transmitter/receiver wrap test failure
• Loss of receive clock
• Loss of transmission clock
• Drive interface hardware error
Table 25 Active LED Out conditions
NORMAL COMMAND ACTIVITY LED STATUS
Spun down and no activity Slow blink (20% on and 80% off a 2 sec cycle)
Spun down and activity (command executing) On
Spun up and no activity On
Spun up and activity (command executing) Off
Spinning up or down Blinks steadily (50% on and 50% off)
Format in progress, each cylinder change Toggles on/off