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i4000 - Quad M-module carrier for VMEbus
User Manual Version: 1.2
AcQuisition Technology bv
P.O. Box 627, 5340 AP
Page 16 of 25 Oss, The Netherlands
4.2. THE INTERRUPTER
The i4000 has a interrupter which is largely compatible with the MC68C153. The interrupter is a so called
D08(O) type interrupter which means that the interrupter during an interrupt acknowledge cycle will put a
status byte on the data lines D0-D7.
The interrupter uses a fixed interrupt level (IRQ1-IRQ7 set by SW1) for all M-modules. The i4000/NP2 also
can be set to “software programmable level”, the interrupt level for an M-module has to be programmed using
the control registers. Each M-module can generate its own vector.
There are two classes of interrupters which are both supported by the i4000: release on acknowledge (ROAK)
or release on register access (RORA). The ROAK interrupter negates its interrupt request line in response to
an interrupt acknowledge cycle. This mechanism will work with all handlers. The RORA interrupter releases
its request when the handler accesses an on-board register during the interrupt service routine. The handler
performs the acknowledge cycle but the interrupter does not immediately negate its request. Sometime during
the service routine the handler will have to write to a register on the interrupter which causes it to negate the
request.
L2 L1 L0 Interrupt level
on on on software programmable level (only i4000/NP2)
on on off level 1
on off on level 2
on off off level 3
off on on level 4
off on off level 5
off off on level 6
off off off level 7
Figure 5 Interrupt request level
Interrupt Level 0x1
1
2
3
4
SW1
Off L0
On L1
On L2
Off Reserved
Example
Off On