Accessing Individual Bits

The mikroC PRO for PIC32 allows you to access individual bits of 32-bit variables. It also supports sbit and bit data types.

Lets use the Sleep bit as an example. This bit is defined in the definition file of the particular MCU as :

const register unsigned short int SLEEP = 3;
sbit  SLEEP_bit at RCON.B1;

To access this bit in your code by its name, you can write something like this:

// Clear Sleep bit 
RCON.SLEEP = 0;

In this way, if Sleep bit changes its position in the register, you are sure that the appropriate bit will be affected.
But, if Sleep bit is not located in the designated register, you may get errors.

Another way of accesing bits is by using the direct member selector (.) with a variable, followed by one of identifiers B0, B1, … , B31, or F0, F1, … F32, with F32 being the most significant bit, to access the desired bit :

// predefined globals as bit designators
// Clear Sleep bit
RCON.B3 = 0;

// Set Sleep bit
RCON.F3 = 1;

In this way, if the target bit changes its position in the register, you cannot be sure that you are invoking the appropriate bit.

This kind of selective access is an intrinsic feature of mikroC PRO for PIC32 and can be used anywhere in the code. Identifiers B0B31 are not case sensitive and have a specific namespace.

You may override them with your own members B0B31 within any given structure.

When using literal constants as bit designators instead of predefined ones, make sure not to exceed the appropriate type size.

Also, you can access the desired bit by using its alias name, in this case Z_bit :

// Set Sleep Bit 
SLEEP_bit = 1;
In this way, if the Sleep bit changes its register or position in the register, you are sure that the appropriate bit will be affected.

For backward compatibility, you can access bits in this way also :

// Clear TRISB3
TRISBbits.TRISB3 = 0;
  Note : If aiming at portability, avoid this style of accessing individual bits, use the bit fields instead.

See Predefined Globals and Constants for more information on register/bit names.

sbit type

The mikroC PRO for PIC32 compiler has sbit data type which provides access to registers, SFRs, variables, etc.
You can declare a sbit variable in a unit in such way that it points to a specific bit in SFR register:

extern sfr sbit Abit; // Abit is precisely defined in some external file, for example in the main program unit

In the main program you have to specify to which register this sbit points to, for example:

sbit Abit at PORTB.B0; // this is where Abit is fully defined
...
void main() {  
...
}

In this way the variable Abit will actually point to PORTB.0. Please note that we used the keyword sfr for declaration of Abit, because we are pointing it to PORTB which is defined as a sfr variable.

  Note : Declaring a sbit variable is not possible via F0, F1, … F31 identifiers.

In case we want to declare a bit over a variable which is not defined as sfr, then the keyword sfr is not necessary, for example:
extern sfr AnotherBit; // AnotherBit is precisely defined in some external file, for example in the main program unit
char MyVar;
sbit AnotherBit at MyVar.B0; // this is where AnotherBit is fully defined
...
void main() {  
...
}

at keyword

You can use the keyword "at" to make an alias to a variable, for example, you can write a library without using register names, and later in the main program to define those registers, for example :

extern char PORTAlias; // here in the library we can use its symbolic name
char PORTAlias at PORTB; // this is where PORTAlias is fully defined
...
void main() {  
...
}
  Note : Bear in mind that when using at operator in your code over a variable defined through a extern modifier, appropriate memory specifer must be appended also.

bit type

The mikroC PRO for PIC32 compiler provides a bit data type that may be used for variable declarations. It can not be used for argument lists, and function-return values.

bit bf;    // bit variable

There are no pointers to bit variables:

bit *ptr;    // invalid

An array of type bit is not valid:

bit arr [5];     // invalid
  Note :
Copyright (c) 2002-2012 mikroElektronika. All rights reserved.
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