Programming the VMEbus Interface
5-3
5
5
VMEbus Master Accesses
The EPC-9 becomes VMEbus Master in the following situations:
1. When the Pentium accesses resources on the VMEbus
2. When the Universe DMA controller performs block-transfer operations.
3. When the Universe generates interrupt-acknowledge cycles as the
VMEbus interrupt handler
4. When the Universe VMEbus ownership bit (VOWN in the MSTR_CTL
register) is set.
The board can perform master accesses in A16, A24 and A32 address spaces using
D08/D16 and D32 data widths. Read accesses to the VMEbus are always coupled,
while write accesses may either be posted or coupled. Write accesses default to
coupled.
The Universe provides four programmable windows into VMEbus memory (PCI
Slave images). The characteristics of the these windows are programmed in the
LSIn_CTL, LSIn_BS, LSIn_BD, and LSIn_TO registers of the Universe chip. Please
refer to the Universe User Manual for programming details.
VMEbus block transfers are supported by the Universe using its on-chip DMA
controller.
The EPC-9 can respond as a VMEbus Slave in either A24 or A32 address spaces. It
responds to either D08, D16 or D32 accesses. Read accesses from the VMEbus to
onboard memory may be either coupled or prefetched (for block transfers), while
write accesses may either be posted or coupled. Both reads and writes default to
coupled.
The Universe provides four programmable windows into PCI memory (VME Slave
images). The characteristics of the these windows are programmed in the VSIn_CTL,
VSIn_BS, VSIn_BD, and VSIn_TO registers of the Universe chip. Please refer to the
Universe User Manual for programming details.
By default, none of the Universe slave images are used or programmed in the EPC-9.
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