User manual

mikoBasic PRO for dsPIC30/33 and PIC24

MikroElektronika

Accessing Individual Bits

The mikroBasic PRO for dsPIC30/33 and PIC24 allows you to access individual bits of 16-bit variables. It also supports

sbit and bit data types.

Lets use the Zero bit as an example. This bit is dened in the denition le of the particular MCU as:

const Z = 1

dim Z_bit as sbit at SR.B1

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

‘ Clear Zero Bit

SR.Z = 0

In this way, if Zero bit changes its position in the register, you are sure that the appropriate bit will be affected.

But, if Zero 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 predened global constants B0, B1, … , B15, or 0, 1, … 15, with 15 being the most signicant bit:

‘ predened globals as bit designators

‘ Clear bit 0 in STATUS register

SR.B0 = 0

‘ literal constant as bit designator

‘ Set bit 5 in STATUS register

SR.F5 = 1

‘ expression as bit designator

‘ Set bit 6 in STATUS register

i = 5

SR.(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 dsPIC30/33 and PIC24 and can be used

anywhere in the code. Identiers B0–B15 are not case sensitive and have a specic namespace.

You may override them with your own members B0–B15 within any given structure.

When using literal constants as bit designators instead of predened 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 Zero Bit

Z_bit = 1

In this way, if the Zero bit changes its register or position in the register, you are sure that the appropriate bit will be affected.

See Predened Globals and Constants for more information on register/bit names.