I/O output

[Manie]

How do I change a single bit value of a port? What is the syntax?

 

[Nigel Goodwin]

How do I change a single bit value of a port? What is the syntax?

Depends what processor you're talking about, and what laguage you're using, your question is far too vague to answer!.

 

[Manie]

I am using a PIC16f737 and programming in C

 

[Nigel Goodwin]

I am using a PIC16f737 and programming in C

Can't help you with C, but in assembler it's simply:

bsf Port, pin

to set a pin high

bcf Port, pin

to clear a pin.

As it's such a basic thing to do, you should have suitable examples with your C compiler?.

 

[akg]

I am using a PIC16f737 and programming in C

port_value = port_value | (1<< bitposition)

or

port_value |= (1<< bitposition)

 

[GraveYard_Killer]

example:

setting PORTB bit 0
PORTB|=(1<<0);

setting PORTB bit 2
PORTB|=(1<<2);


clearing PORTB bit 2
PORTB&=~(1<<2);

 

[Papabravo]

Check your C-compiler. Many of them have a declaration syntax for bits. If they do then the statement is just something like

bit  GIE  INTCON.7

GIE = 0 ; /* Disable Interrupts */
...
GIE = 1 ; /* Enable Interrupts */

The declaration syntax is not part of the C language standard, but several compilers for processors that support bit addressing have invented such extensions. You do have to look carefully in the compiler documentation though.

Look for #pragma keyword=extended or something similar to see if there is a switch that enables or disables the extended language features.

If you think you've found something then write a short test program and look at the compiler output to see if it matches both your understanding and Nigel's example.

On real ports with a mixture of inputs and outputs you need to be careful with bsf and bcf instructions because in hardware they read all 8 bits of a port, modify the single bit, and write back all 8 bits. This can be problematic and there are warnings in the PIC data sheets.

Let us know what you find.