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NAME

SetIntVector
set a new handler for a system interrupt vector

SYNOPSIS

oldInterrupt = SetIntVector(intNumber, interrupt)
D0 D0 A1

struct Interrupt *SetIntVector(ULONG, struct Interrupt *);

FUNCTION

This function provides a mechanism for setting the system interrupt vectors. These are non-sharable; setting a new interrupt handler disconnects the old one. Installed handlers are responsible for processing, enabling and clearing the interrupt. Note that interrupts may have been left in any state by the previous code.

The IS_CODE and IS_DATA pointers of the Interrupt structure ('C': is_Code and is_Data) will be copied into a private place by Exec. A pointer to the previously installed Interrupt structure is returned.

When the system calls the specified interrupt code, the registers are setup as follows:

D0 - scratch
D1 - scratch (on entry: active
interrupts -> equals INTENA & INTREQ)

A0 - scratch (on entry: pointer to base of custom chips
for fast indexing)
A1 - scratch (on entry: Interrupt's IS_DATA pointer)

A5 - jump vector register (scratch on call)
A6 - Exec library base pointer (scratch on call)

all other registers must be preserved

INPUTS

intNum
the Paula interrupt bit number (0..14). Only non-chained interrupts should be set. Use AddIntServer() for server chains.

interrupt
a pointer to an Interrupt structure containing the handler's entry point and data segment pointer. A NULL interrupt pointer will remove the current interrupt and set illegal values for IS_CODE and IS_DATA.

By convention, the LN_NAME of the interrupt structure must point a descriptive string so that other users may identify who currently has control of the interrupt.

RESULT

A pointer to the prior interrupt structure which had control of this interrupt.

SEE ALSO

AddIntServer(), "exec/interrupts.i", "hardware/intbits.i", <exec/interrupts.h>, <hardware/intbits.h>