Artesyn BajaPPC-750, Руководство пользователя

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6-26 BajaPPC-750: VMEbus Interface
May 2002
AM0-AM5 ADDRESS MODIFIER (bits 0-5). Three-state lines that are used to broad-
cast information such as address size and cycle type.
AS* ADDRESS STROBE. A three-state signal that indicates when a valid
address has been placed on the address bus.
BBSY* BUS BUSY. An open-collector signal driven low by the current master to
indicate that it is using the bus. When the master releases this line, the
resultant rising edge causes the arbiter to sample the bus request lines
and grant the bus to the highest priority requester. Early release mode is
supported.
BCLR* BUS CLEAR. A totem-pole signal generated by the arbiter to indicate
when there is a higher priority request for the bus. This signal requests
the current master to release the bus.
BERR* BUS ERROR. An open-collector signal generated by a slave or bus timer.
This signal indicates to the master that the data transfer was not com-
pleted in the time alloted (64 or 128µs).
BG0IN*-BG3IN* BUS GRANT (0-3) IN. Totem-pole signals generated by the arbiter and
requesters. Bus-grant-in and bus-grant-out signals form bus grant daisy
chains. An input to the BajaPPC-750, the bus-grant-in signal indicates
that it may use the bus if it wants.
BG0OUT*-BG3OUT* BUS GRANT (0-3) OUT. Totem-pole signals generated by requesters. An
output from the BajaPPC-750 (driven by boards not requesting the bus,
in response to the bus-grant-in signals), the bus-grant-out signal indi-
cates to the next board in the daisy-chain that it may use the bus.
BR0*-BR3* BUS REQUEST (0-3). Open-collector signals generated by requesters.
Assertion of one of these lines indicates that some master needs to use
the bus.
D00-D31 DATA BUS. Three-state bidirectional data lines used to transfer data
between masters and slaves.
DS0*, DS1* DATA STROBE ZERO, ONE. A three-state signal used in conjunction with
LWORD* and A01 to indicate how many data bytes are being transferred
(1, 2, 3, or 4). During a write cycle, the falling edge of the first data strobe
indicates that valid data are available on the data bus.
DTACK* DATA TRANSFER ACKNOWLEDGE. Either an open-collector or a three-
state signal generated by a slave. The falling edge of this signal indicates
that valid data are available on the data bus during a read cycle, or that
data have been accepted from the data bus during a write cycle. The ris-
ing edge indicates when the slave has released the data bus at the end of
a read cycle.