Motorola MVME2400 - Manual (Page 82)

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Programming the MVME240x
4
Programming Considerations
Good programming practice dictates that only one MPU at a time have
control of the MVME240x control registers. Of particular note are:
❏ Registers that modify the address map
❏ Registers that require two cycles to access
❏ VMEbus interrupt request registers
PCI Arbitration
There are seven potential PCI bus masters on the MVME240x :
❏ Hawk ASIC (MPU/PCI bus bridge controller)
❏ Winbond W83C553 PIB (PCI/ISA bus bridge controller)
❏ DECchip 21143 Ethernet controller
❏ UniverseII ASIC (PCI/VME bus bridge controller)
❏ PMC Slot 1 (PCI mezzanine card)
❏ PMC Slot 2 (PCI mezzanine card)
❏ PCI Expansion Slot
The Winbond W83C553 PIB device supplies the PCI arbitration support
for these seven types of devices. The PIB supports flexible arbitration
modes of fixed priority, rotating priority, and mixed priority, as
appropriate in a given application. Details on PCI arbitration can be found
in the MVME2400-Series VME Processor Module Programmer’s
Reference Guide.