Yamaha MTX Series Setup Manual page 56

2.
Specify the number of units that will be connected in your MTX/MRX System, and click
[Next>].
Specify "2" as the number of "YDIF Connected" MTX3 units, specify "1" as the number of "ANALOG Connected"
XMV4280, and specify "1" as the number of MCP1.
3.
Specify the YDIF MODE to CASCADE, and then click [Next>].
A dialog box will appear when you change this to CASCADE; click [OK].
Unless you have specific reasons for doing so, use the UNIT ID that is assigned.
In this example, set the XMV's UNIT ID to 1A so that we can explain how to change the UNIT ID.
Example 3) Using cascade mode to add MTX input channels (analog connection)
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MTX Setup Manual