RK06/RK07 Disk Drive User's Manual - Trailing-Edge

6.2.3 UNIT SELECT Switch with READY Indicator
The UNIT SELECT switch is a cam-operated assembly that is actuated by the insertion of a plastic
plug. The face side of each actuator plug contains a single number (0-7), while the other side consists of
raised plastic cam actuators that are separately configured to encode the plug with the number. With
this arrangement, the: insertion of a plug into any UNIT SELECT switch assembly will automatically
encode the associated! plug number when power is applied to the drive. When the heads of a drive are
settled (not in motion), the numbered indicator on the UNIT SELECT switch assembly associated
with the drive is illuminated (READY).
6.2.4 FAULT Indicator
The FAULT indicator is illuminated whenever one of the following error conditions is detected in the
drive:
• More than one drive selected.
• Positioner, when detented, has moved too far (e.g., the drive has been jarred).
• A parity error has occurred in a message transmitted from the controller to the drive.
• A read/write unsafe condition in the drive (e.g., serve track error signals, write gate signal
errors, etc.)
• A write lock error condition (i.e., the receipt of a Write Gate signal when the drive is in Write
Protect mode).
• Low ac voltage in the drive.
• An incomplet,e Seek operation.
• The receipt of Write Gate or Seek signals while Volume Valid is reset.
6.2.5 WRITE PROT Switch with PR OTECT Indicator
If a Write Gate signal from the controller is not currently asserted in a selected drive, initial depression
of the WRITE PROT pushbutton will immediately set the drive in Write Protect mode, and the
PROTECT indicator will be illuminated. When the alternating action pushbutton is again pressed,
write protection is removed and the PROTECT indicator is extinguished. However, if a Write Gate
signal is asserted in the selected drive when the switch is initially pressed, write protection will be
inhibited and the PROTECT indicator will remain extinguished until the Write Gate signal is negated.
Once the Write Gate signal is negated, the Write Protect mode is entered and the PROTECT indicator
is illuminated.
6.2.6 ACCESS A ENABLE Switch with SELECT Indicator
The ACCESS A ENABLE switch is an alternating action pushbutton that is found on both singleaccess
drives (Access A or Access B) and drives containing the dual-access option (Port A and Port B).
6.2.6.1 Single-Acces!!t Drive (A) - If Port A is configured for single access (i.e., the M7706 Interface
and Timing Module is in Slot 3 of the drive card cage) and the switch is initially depressed, bidirectional
communication with the controller is enabled via Port A. Under these conditions, when the
drive is selected by the controller, the SELECT A indicator is illuminated. When the switch is again
depressed (released), access by the controller is disabled and the SELECT A lamp cannot be illuminated.
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