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#FAST_IO directive

 
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ibg



Joined: 19 Nov 2003
Posts: 22

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#FAST_IO directive
PostPosted: Fri Jan 09, 2004 11:38 am     Reply with quote
I�ve read in the CCS manual that the #FAST_IO directive affects how the compiler will generate code for input and output instrucctions.

It�s also said that the fast method of doing I/O will cause the compiler to perform I/O without programming of the direction register.

What does all the above mean? What happen if we don�t specify the #fast_io directive for a certain port? How the I/O is done then?

Thanks for all,

Imanol
Neutone



Joined: 08 Sep 2003
Posts: 839
Location: Houston

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Re: #FAST_IO directive
PostPosted: Fri Jan 09, 2004 12:14 pm     Reply with quote
ibg wrote:
I�ve read in the CCS manual that the #FAST_IO directive affects how the compiler will generate code for input and output instrucctions.

It�s also said that the fast method of doing I/O will cause the compiler to perform I/O without programming of the direction register.

What does all the above mean? What happen if we don�t specify the #fast_io directive for a certain port? How the I/O is done then?

Thanks for all,

Imanol


Each pin can be either an input or an output but not both at the same time. If you have a pin that will only be used as an output it may be set as an output only once instead of every time the output value is changed. If you use a pin as both an input and an output the pin must be specified as an output or an input before each read or write to the pin.

#standard_IO is the default and it will specify the direction (in or out) before you use the pin, each time you use it.
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