A software interrupt is requested by the program through int. This complete example installs a handler, requests an interrupt, and resumes at halt:

.section my_code
    ld $handler, %r1
    csrwr %r1, %handler
    int
    halt
handler:
    ld $42, %r5
    iret
.end

The emulator sets a pending software flag when it executes int. Its following interrupt check builds the frame, writes cause four, and transfers to the installed handler. The handler leaves forty-two in %r5; iret restores the saved state and returns to the instruction following int.

Software delivery does not require -timer or -terminal. Those options enable host-generated device events, not the program's own request.

In this implementation the software case does not consult the timer, terminal, or global hardware-mask bits. Do not assume that setting the global status mask blocks every interrupt kind. The handler and internal interrupt-enable checks still apply to delivery.

Source: emulator.c.