Now, after reading it, I have one question you might be able to explain.
It says the following:
Hence, location 1 must contain the start address of the interrupt handler. When an interrupt happens, further interrupts are disabled until they are explicitly re-enabled. A return from the interrupt is performed by jumping indirectly through location zero (i.e. JMP @0).
Earlier in the document, it's explained that interrupts are enabled using the INTEN instruction, so if I read the correctly, the end of the interrupt handler should be an INTEN followed by JMP @0.
But what happens if there is another interrupt after enabling it, but before the jump is done?