Publication No. PPC11A-HRM/1
Functional Description 37
4.9.2 VMEbus Master Access
Five general-purpose, software programmable PCI slave images are available for
access to the VMEbus. These can all be configured to access VME A32, A24 or A16
address space. An offset may be applied to translate the local address to a different
address on the VMEbus, allowing any local address to access any VMEbus address.
The VME window size can be set to 16, 32, 64, 128, 256, 512, 1024 or 2048 MB.
VMEbus master cycles may be coupled or write posted. Coupled cycles are retried
on the PCI bus until the Universe II has ownership of the VMEbus and are not
terminated on the PCI bus until all data has been transferred over the VMEbus.
Posted writes are queued in a FIFO until the VMEbus is available for the data to be
transferred.
4.9.3 VMEbus Slave Access
Eight general-purpose, software programmable VMEbus slave images are available.
These may all be defined in VME A32, A24 or A16 space. An offset may be applied
to translate the VMEbus address to a different address on the local bus, allowing any
VMEbus address to access any on-board address. The start address and size of
window are programmable.
VMEbus slave accesses to the PPC11A may be coupled, write posted or pre-fetched
block read. Coupled slave transfers can only proceed once the slave posted write
FIFO is empty. Slave posted write cycles are queued in a FIFO until the PCI bus is
available for the data to be transferred.
4.9.4 Indivisible cycles on VME
The Universe II chip may be programmed to generate RMW cycles on the VMEbus.
The Universe II chip’s VMEbus ownership-bit may be set (VME Request control
register) to cause it to acquire and hold ownership of the VMEbus.
4.9.5 VMEbus Arbitration and Slot 1 functions
The Universe II chip’s VMEbus arbiter supports PRI and RRS arbitration with
BCLR~ generation in priority mode. The VMEbus requester may operate in fair or
demand mode and may be configured as RWD or ROR.
The following Slot 1 functions are also provided:
•
SYSCLK driver
•
IACK daisy chain driver
•
VMEbus timer (disabled, 16, 32, 64, 128, 256, 512, 1024
µ
s)
Содержание PPC11A
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