USE of #use fixed_io

[cf]

Hi,

Who can explain me how to use #use fixed_io.

I'm see that if i'm want to use 232 and I2C i'm must do

#use delay(clock=xxxxxxx)

#use rs232(baud=9600,xmit=PIN_C6,rcv=PIN_C7,parity=N,bits=8,xxxxx)
#use I2C(master, sda=PIN_C4, scl=PIN_C3)

and if i'm want to work with an over bit on port C as output

#use fixed_io(c_outputs=PIN_C0)

but now if i'm want to use an over pin PIN_C2 as input what must i do

generaly i'm use this kind of funtion to initialise my port :

/**************************************/
/* initialisation du port J en sortie */
/**************************************/
void ini_outpj (void)
{
//clear portg
output_J(0);
//direction en sortie
set_tris_J(0X00);
}
/**************************************/
/* initialisation du port J en entre */
/**************************************/
void ini_outpj (void)
{
//clear portg
output_J(0);
//direction en entre
set_tris_J(0XFF);
}


thank

c.f

[Mark]

Straight from the help file

[Ttelmah]

As has been pointed out by another poster, the manual does cover this pretty well. However it is worth pointing out firstly, that in the code you post, the 'tris_J' statement, effectively acomplishes nothing, unless you are selecting fast_io or fixed_io.
Basically, with the default setting, if you output to a port bit, the compiler automatically clears the corresponing TRIS bit (making the pin an output), and costing one instruction to do it, then outputs the bit. If instead you perform an input on a pin, the compiler instead sets the corresponding TRIS bit, and then reads from the pin. With both 'fixed_Io', and 'fast_IO', this automatic behaviour is turned off. With the latter it is completely disabled for the port, requiring you to have a tris control instruction, but with the former, the 'pin' definitions in the statement, are applied to the TRIS register at that point in the code, and remain in force till either a different 'fixed_IO' statement changes it, or you use TRIS. The default form is bulkier, but has the advantage of allowing 'psuedo tri-state' operation on the pins. With this form, you can leave the compiler to control TRIS for you as needed.

Best Wishes

[cf]

Hi,

Thank for your answser.

I'm not understand all, so my question was not the good question.

My problem is how to use a demo board whith PIC18F8720 and have the possibility of use or not use hardware resouces implant on it :

RS232 driver tx:PIN_C6, rx:PIN_C7,cts:PIN_B2,rts:PIN_B1

Temperature sensor scl:PIN_C3,sda:PIN_C4

In all case these pin must be affected in the good direction for not have electrical problem


if i'm not use the directive
#use rs232(baud=2400, xmit=PIN_C6, rcv=PIN_C7)
#use I2C( xxxx, scl=PIN_C3,sda=PIN_C4)

i'm can use #use fast_io(C) and SET_TRIS_C( xxx ) to have alway the pin in the good direction.

if i'm use only the directive #use rs232(baud=2400, xmit=PIN_C6, rcv=PIN_C7)

what must i'm do to put PIN_C3 and PIN_C4 for ever in the good direction ?

how work a#use RS232 directive ? it is the complier provide code for input and output.

If i'm use #use fast_io(C) is it in contradiction whith the #use RS232

Or simply i'm can do that an set the tris register for
C3 and C4 in the direction what i'm want to use
C6 and C7 in correspondance with the #use RS232 ?


thank

C.F