What is an injection channel used for in a SAR A2D?

[SuzyC]

The PSoC4 MCU's have SAR's that have multi-channel input and one injection channel.
ummm...whats that for?

[nuno]

They explain that in one of the docs. Basically and if I remember correctly, you can have the ADC automatically doing readings round-robin on a set of channels. It happens that sometimes you want to do an odd reading on channel which is not part of the set, or a channel you want to just read at a much lower pace; the hw allows you to do this, to inject a one-time "foreign" channel reading in the reading loop programmed in the hw.

[SuzyC]

Thanks nuno, for the explanation, it will help me to work with this a2d module.