Requirements when C<5, Dimensionality = 0 and Throughput > 1

[matthijsr]

Background

https://abs-tudelft.github.io/tydi/specification/physical.html#signal-omission

Specifies that:

• stai is contingent on C≥6∧N>1
• endi is contingent on (C≥5∨D≥1)∧N>1
• strb is contingent on C≥7∨D≥1

Potential Issue

As a result of these requirements, a Stream with C<5, D=0 and element lanes N>1 should not have an endi signal.
This means that all lanes in a transfer must be valid, as there is no way to set individual lanes as being inactive.

Suggested Fix

The current specification implies that any transfer with C<5, D=0, N>1 must consist of Q elements where Q mod N = 0.

It is not clear whether this is intentional, I can think of two other ways in which to make behavior consistent:

1. N>1 is contingent on D>0∨C≥5 - i.e., it is not allowed to transfer multiple elements at the same time except in a list or at higher complexities.
2. endi is solely contingent on N>1 - i.e., it is always allowed to transfer multiple elements, and endi can be used to encode lane validity when sequences do not align to the number of element lanes.