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EPC-9 Hardware Reference
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VMEbus Locked Accesses (RMW)
Each of the four PCI Slave images support VMEbus Read-Modify-Write (RMW)
cycles, if so programmed. This causes a non-block VMEbus RMW read cycle to
generate a coupled PCI locked read cycle. PCI ~LOCK is then asserted on the PCI
bus until AS* is negated on the VMEbus.
VMEbus Interrupter
The Universe VME controller provides a flexible scheme to map interrupts to either
the PCI bus or the VMEbus. This mapping is controlled in the LINT_EN,
LINT_MAP0, LINT_MAP1, VINT_EN, VINT_MAP0, and VINT_MAP1 registers.
The following interrupts can be mapped to any of the VMEbus IRQ* pins.
•
PCI bus errors
•
VMEbus errors
•
DMA interrupts
•
Software interrupts
If a software and a hardware source are both mapped to the same IRQ*, the software
source has higher priority.
When an IACK cycle on the VMEbus is detected that matches an interrupt level that
the EPC-9 is asserting (and the IACKIN daisy chain is asserted into the EPC-9), the
Universe responds by supplying an 8-bit STATUS/ID vector. This vector is
programmable through the STATID register. When the IACK cycle is complete, the
Universe releases the VMEbus and the interrupt vector is passed to the PCI master
(Pentium). Software interrupts are Release-On-Acknowledge (ROAK), while
hardware and internal interrupts are Release-On-Register-Access (RORA).
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