VMEbus Control Signals
6-27
IACK*
INTERRUPT ACKNOWLEDGE. An open-collector or three-state signal
used by an interrupt handler acknowledging an interrupt request. It is
routed, via a backplane signal trace, to the IACKIN* pin of slot one,
where it forms the beginning of the IACKIN*-IACKOUT* daisy-chain.
IACKIN*
INTERRUPT ACKNOWLEDGE IN. A totem-pole signal and an input to
the BajaPPC-750. The IACKIN* indicates that the board may respond to
the interrupt acknowledge cycle that is in progress. Address lines A3–A1
carry the associated interrupt request level.
IACKOUT*
INTERRUPT ACKNOWLEDGE OUT. A totem-pole signal and an output
from the BajaPPC-750. The IACKIN* and IACKOUT* signals form a daisy-
chain. The IACKOUT* signal indicates to the next board in the daisy-
chain that it may respond to the interrupt acknowledge cycle in
progress.
IRQ1*-IRQ7*
INTERRUPT REQUEST (1-7). Open-collector signals, generated by an
interrupter, which carry interrupt requests. When several lines are moni-
tored by a single interrupt handler, the line with the highest number is
given the highest priority.
LWORD*
LONG WORD. A three-state signal used in conjunction with DS0*, DS1*,
and A01 to select which byte location(s) within the 4-byte group are
accessed during the data transfer. It is also used for D64 transfers.
RETRY*
RETRY. A line driven by a Slave to indicate to the Master that the cycle
cannot be completed and the Master should try again later. This signal is
not implemented on the BajaPPC-750.
SERCLK
SERIAL CLOCK. A totem-pole signal that is used to synchronize the data
transmission on the VMEbus. This signal is not implemented on the
BajaPPC-750.
SERDAT*
SERIAL DATA. An open-collector signal that is used for VMEbus data
transmission. This signal is not implemented on the BajaPPC-750.
SYSCLK
SYSTEM CLOCK. A totem-pole signal that provides a constant 16-MHz
clock signal that is independent of any other bus timing. This signal is
driven if the BajaPPC-750 is a system controller.
SYSFAIL*
SYSTEM FAIL. An open-collector signal that indicates a failure has
occurred in the system. It is also used at power-up to indicate that at least
one VMEbus board is still in its power-up initialization phase. This signal
may be generated by any board on the VMEbus. The Universe drives this
signal low at power-up. On the BajaPPC-750, SYSFAIL* may be driven by
the board, and it is possible to read the state of the VMEbus SYSFAIL* sig-
nal.
SYSRESET*
SYSTEM RESET. An open-collector signal that, when asserted, causes the
system to be reset.
Содержание BajaPPC-750
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