Quote:
Originally Posted by project23
So I take it the int2 line is useful for filesystem access and the like?
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The INT2 cable is optional.
What happens is the following: when a314d sends a packet to the Amiga, a314d writes the packet to the com-area, and then writes to a CMEM register (A_EVENTS) to set a bit (A_EVENT_R2A_TAIL) that signals that a new packet has been written. This will make the INT2 pin active (driven low). If an INT2 cable is attached, Paula will notice this and invoke the shared INT2 interrupt handler, which calls the
interrupt server of a314.device. The interrupt server will read and clear A_EVENTS, and the INT2 pin will then stop being driven low.
If no INT2 cable is attached then the a314.device interrupt server will instead be invoked by the VBlank interrupt handler, which fires once every 20 ms. The effect (of not having an INT2 cable) is that the delay from when a314d writes a packet until a314.device notices that will be somewhere between 0 to 20 ms. By attaching the INT2 cable there is no such delay.
Quote:
Originally Posted by project23
I was wondering how that was implemented.
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I realize now that I should really write a document that describes this
In the mean while you could look at the source code and if you have any specific questions feel free to ask here or pm me.