How fast can it be to forward the digital value of pin A to another pin B?

Projects Programming
1

I am trying to use Arduino as a multiplexer.

Basically, it should choose a number of input signals all running at 125Kbps to a single output pin 'B'. The reading instance can be specified by the interrupt from an external clock also running at 125KHz from the same SPI interface of the input signals.

Is that possible to finish the tasks in 8us?

Any suggestion to speed it up and make it reliable?

2

Any suggestion to speed it up and make it reliable?

Speeding code up will not make it more reliable.

"Direct port manipulation" is the google phrase-of-interest.

3

zcambridge:
Any suggestion to speed it up and make it reliable?

Use a hardware multiplexer (controlled by your Arduino).

4

Basically, it should choose a number of input signals all running at 125Kbps to a single output pin 'B'.

How many input signals? Are you trying to develop a parallel to serial interface?

As Paul S suggested, a key to this is to organize the input on pins common to a register port.

Is that possible to finish the tasks in 8us?

Since most of the PORT reading and writing commands are 1 clock cycle, you can get a lot done in 128.