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38 PPC11A 6U VME Single Board Computer
Publication No. PPC11A-HRM/1
4.9.6 VMEbus Master Block Transfers (DMA)
The Universe II chip’s DMA controller may be used to transfer data between the PCI
bus and the VMEbus. DMA operations on the two buses are decoupled through a bi-
directional FIFO. The DMA controller can generate an interrupt on completion or on
encountering an error condition.
4.9.7 VMEbus Slave Block Transfers
The VMEbus slave interface can respond to D32:BLT and D64:MBLT. For VMEbus
slave block transfers, the Universe II chip may be programmed to pre-fetch read
data, which is queued in a FIFO.
4.9.8 VMEbus Interrupts
If programmed to do so, the Universe II responds to a VMEbus interrupt with a
VMEbus interrupt acknowledge cycle. The Universe II captures the status/ID and
then raises an interrupt on the PCI bus. No further VMEbus interrupts are handled
on that level until the processor reads the status/ID and re-arms the interrupt
handler.
The Universe II can be programmed to generate any level of VMEbus interrupt. It
can raise an interrupt on the PCI bus when the VMEbus interrupt has been
acknowledged.
Seven software interrupts in the Universe II allow an interrupt to be generated on
any of the seven VMEbus IRQs.
4.9.9 VMEbus Errors
Assertion of BERR~ during a coupled VMEbus master cycle causes a target-abort
(bus error) on the PCI bus. A PCI bus target-abort during a coupled VMEbus slave
cycle causes BERR~ on the VMEbus.
A bus error during posted write transfers raises an interrupt (if enabled) to the
processor. Several options are available, including stopping the operation and
purging the offending transaction.
A bus error during a DMA operation raises an interrupt and stops the DMA
operation on the bus where the error was detected.