VIC: Synchronous vs asynchronous modes

I'm trying to understand the two modes of Vectored Interrupt Controller (PL192) and have some difficulty understanding it from a programmer's perspective. As a, standalone interrupt controller for a ARM Cortex R5 cpu, do these two modes matter ? I was wondering if someone can give some high level information about these two modes, configuring the two modes and pros and cons of each modes. 

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