User manual

The example above shows that the CHARON core is not obliged to support the indicated

operation. It also indicates why the device instance should remember the chapi_in

descriptor.

4.9.4 Enable/disable bus request

The operation of enabling/disabling a bus request belongs to the group of operations

previously called “Request for bus interrupt”. Such an operation is initiated by the device

instance and CHARON core is defined as the target of the operation. Actually the CPU

instruction interpretation thread is supposed to respond to the bus request

enabling/disabling. When particular bus request is disabled it is just ignored by the bus

server when set and processed and the same situation when enabled.

In order to perform the operation, the initiator invokes a routine identified by the

enable_bus_request field of the chapi_in descriptor supplying in the parameter brq_handle the

identifier of bus request to enable/disable and in the parameter enable the type of

operation (true – enable, false - disable). The procedure is invoked as follows:

brq_handle_t brq_handle;

const chapi_in * ci = …;

…

// Connect bus request to the bus getting brq_handle as in previous example

…

// Lets assume that some kind of interrupt enable bit is updated for

// the device and (CSR & IE_BIT) give us the new value…

if (ci->enable_bus_request) {

ci->enable_bus_request(ci, brq_handle, CSR & IE_BIT);

}

The example above shows that the CHARON core is not obliged to support the indicated

operation. It also indicates why the device instance should remember the chapi_in

descriptor.

4.9.5 Get interrupt vector

The operation of getting an interrupt vector belongs to the group of operations previously

called “Request for a bus interrupt acknowledge”. Such an operation is initiated by the

device instance and CHARON core is defined as the target of the operation. This routine

should be used to get appropriate interrupt vector for the bus server using particular

emulated device interrupt vector – these vector can be different, e.g. for the VAX QBUS

system appropriate interrupt vector which should be passed to the bus server is calculated

as <emulated_device_interrupt_vector> + 0x200.

In order to perform the operation, the initiator invokes a routine identified by the get_vector

field of the chapi_in descriptor supplying in the parameter vector the vector in terms of

emulated device. The procedure is invoked as follows:

// The common place to use get_vector routine is bus request