Arm7+transfer speed

And the OP wants eight such interfaces...

Of course. But you wouldn't run the 8 channels one at a time in sequence, would you?

One write can toggle the clock for all eight channels (one or eight pins depending on how the external hardware is connected).
One read can fetch one bit each from eight channels.
One more write to toggle the clock line again.

Obviously extra (tabulated) instructions are needed if the user wants to demultiplex the received channels, but to minimize the task for the microcontroller we assumes that we pick up the data with each bit in a byte representing one channel, and that we forward the data in the same way.

And the OP wants eight such interfaces...

Of course. But you wouldn't run the 8 channels one at a time in sequence, would you?

One write can toggle the clock for all eight channels (one or eight pins depending on how the external hardware is connected).
One read can fetch one bit each from eight channels.
One more write to toggle the clock line again.

Obviously extra (tabulated) instructions are needed if the user wants to demultiplex the received channels, but to minimize the task for the microcontroller we assumes that we pick up the data with each bit in a byte representing one channel, and that we forward the data in the same way.