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8.4 INTERFACE
The dual-port read/write cable (cable B) is identical to the standard D2246 cable B. The
dual-port control cable (cable A), however, provides one additional status line. This line,
Busy, issues a status reponse to a controller attempting to select a reserved or selected
drive.
8.5 STATUS COMMANDS
The Dual-Port Interface provides two additional status commands.
8.5.1 Release Command
This command (bus bit 9 and Tag 3) is transmitted to the drive from the controller. It
releases controller reserve and priority select, freeing the drive for use by the other
controller.
8.5.2 Priority Select
The Priority Select signal (bus bit 9, Unit Select lines, and Unit Select Tag) is issued by a
controller. This signal forces the drive to become unconditionally selected and absolutely
reserved by the controller issuing the Priority Select signal. While this signal is active, the
second controller is denied access to the drive. A Priority Select signal is not disabled by
the release timer function.
8-4
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