set_tris questions

[liche]

I'm a bit confused on when to use the set_tris statements for various type of i/o configurations such as Standard IO, Fast IO, etc...

Is it necessary to use the set_tris statements for all of these types of I/O or only on some types?

Thanks
___________________________
This message was ported from CCS's old forum
Original Post ID: 14003

[david smith]

:=I'm a bit confused on when to use the set_tris statements for various type of i/o configurations such as Standard IO, Fast IO, etc...

Somebody may offer better info, but I believe...

STANDARD_IO (default) doesn't require SET_TRIS, and sets direction each instance of an IO cmd.

I use FAST_IO and Set_TRIS on projects to run faster and with less RAM.

On most of my projects, the use of the pin never changes.
In a current project, I use PORTB as a bidirection bus to external parallel registers, so I've defined constants for
bus direction.

Example:

#USE FAST_IO(B) // Use TRIS fctns to set dir of I/O

// Data bus is B, and is bidirectional
#BYTE BUS_RD = 0xFF // tris register values for reading
#BYTE BUS_WR = 0x00 // for writing

//*** write to bus routine
int8U wr_ext(int8U addr, int8U data) {
// not shown: set address
SET_TRIS_B(BUS_WR); // set bus direction
PORTB = data; // put data on data bus [B]
WR = 1; // generate wr pulse
WR = 0;
SET_TRIS_B(BUS_RD); // set bus direction
}
___________________________
This message was ported from CCS's old forum
Original Post ID: 14015