Accessing Individual Bits

The mikroBasic PRO for PIC32 allows you to access individual bits of 16-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 SLEEP = 3
dim   SLEEP_bit as sbit at RCON.B3

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 a primary expression. Primary expression can be variable, constant, function call or an expression enclosed by parentheses. For individual bit access there are predefined global constants B0, B1, … , B15, or 0, 1, … 15, with 15 being the most significant bit :

' predefined globals as bit designators
' Clear bit 0 in RCON register 
RCON.B0 = 0

' literal constant as bit designator
' Set bit 5 in RCON register 
RCON.F5 = 1

' expression as bit designator
' Set bit 6 in RCON register 
i = 5
RCON.(i+1) = 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 mikroBasic PRO for PIC32 and can be used anywhere in the code. Identifiers B0–B15 are not case sensitive and have a specific namespace.

You may override them with your own members B0–B15 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.

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

sbit type

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

module MyModule
   
dim Abit as sbit sfr external ' Abit is precisely defined in some external file, for example in the main program unit
...
implements
....
end.

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

program MyProgram
...
dim Abit as sbit at PORTB.0 ' this is where Abit is fully defined
...
main:
...
end.

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.
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:

module Mymodule
   
dim AnotherBit as sbit external ' Abit is precisely defined in some external file, for example in the main program unit
...
implements
...
end.

program MyProgram
...
dim MyVar as byte
dim Abit as sbit at MyVar.0 ' this is where Abit is fully defined
...
main:
...
end.

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 :

module MyModule
   
dim PORTAlias as byte external ' here in the library we can use its symbolic name
...
implements
...
end.

program MyProgram
...
dim PORTAlias byte as at PORTB ' this is where PORTAlias is fully defined
...
main:
...
end.

Note : Bear in mind that when using at operator in your code over a variable defined through a external modifier, appropriate memory specifer must be appended also.

bit type

The mikroBasic 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.

dim bf as bit  ' bit variable

There are no pointers to bit variables:

dim ptr as ^bit     ' invalid

An array of type bit is not valid:

dim arr as array[5] of bit     ' invalid

Note :

Bit variables can not be initialized.
Bit variables can not be members of structures.
Bit variables do not have addresses, therefore unary operator @ (address of) is not applicable to these variables.

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