Motorola MVME147 Installation And Use Manual page 105

Programming the VMEchip
When the bits are set to drive one of the IRQ lines, they
Note
must not be changed. The three bits may be changed
only when they are all cleared, signifying that the
previous interrupt request has been serviced.
An added function provided by setting IACKEN (refer
to the Utility Interrupt Mask Register section in this
4
chapter) is provided by the VMEchip to signal the local
processor when the interrupt request (generated
through this register) has been acknowledged on the
VMEbus.
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