SCSP slots with multiple inputs in FM mode

[mic]

The SCSP manual isn't very clear on this (or anything else for that matter )...

It's possible to use more than one slot as input for another slot, as shown in the example. Since each slot only has a single MDXSL/MDYSL pair, how would you actually go about setting more than one slot as input? The manual talks about "when slot 0 is input" and "when slot 1 is input", but I want them both to be inputs at the same time so that I can make connections like these:

Or am I supposed to switch the MDXSL/MDYSL values really fast? Because that would be pretty annoying.

 

[antime]

As I understand it, in FM mode every slot always has two modulation sources. The X and Y modulation sources are given as signed numbers relative to the current slot with zero meaning self-modulation. This is complicated a bit by the fact that the modulation sources actually refer to locations on the sound stack which holds two generations of output samples. Table 4.16 shows the value to put into MDXSL/MDYSL for every combination of slot and modulation source and sample generation.


A further wrinkle is the pipelined nature of the SCSP which introduces a six-cycle latency (according to the document) until the slot data is written to the sound stack. This means that eg. if slots 2 and 20 both use slot 0 as modulation source they will sound a bit different even if they are otherwise identically configured as slot 0's output hasn't been written to the stack when slot 2 reads the stack.