U[0..n]=(peripheral aaaa input from command cc); V=n

This is called the Channel In instruction. It results in a variable number of bytes being sent by the peripheral and stored in U starting at U(0). The number of bytes transferred is determined by the peripheral, and will be between 0 and 20, unless the firmware was built after 10 Jan 2020, in which case it needs to be less than 250. The byte count is stored in V.

There are 16 allowable command codes, so this instruction could address 16 long source registers, for example display lines on a text display.

This is a low-level instruction associated with the SPLat Expansion Framework. You will most likely never need to know how to use it.

See also Error handling in SPx transfer instructions