#use fast_io

[Monica]

Dear all,

What is the major difference between:
using fast_io and without fast_io?

Is it because, while adding this line, the output will be faster?

Thanks.

Monica
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[Pete Smith]

:=Dear all,
:=
:=What is the major difference between:
:=using fast_io and without fast_io?
:=
:=Is it because, while adding this line, the output will be faster?

Yes and no :-)

By default, the CCS compiler will set the TRIS registers on the fly, so if you do temp=input(PIN_A1); it will set the TRIS_A register to make A1 an input. If you then do output_high(PIN_A1), it will change the tristate register to make A1 an output.

The downside of this is that every time you use an I/O pin, the tristate registers are messed round with, which in principle, could make I/O slower, but not much. It also uses more ROM.

If you #use fast_io, you've got to set your own tristate registers. The advantages are that you have more control, and your code is smaller.

FWIW, you can find this information on page 46 (for Fast IO) on the latest CCS C Manual

Hope this helps,

Pete.
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This message was ported from CCS's old forum
Original Post ID: 9756