ZBasic System Library
279
ZBasic Microcontrollers
Type
Subroutine
Invocation
SetBits(target, mask, value)
Parameter
Method
Type
Description
target
ByRef
Byte
The byte to be modified.
mask
ByVal
Byte
The mask indicating which bits to modify.
value
ByVal
Byte
The value of the bits to store.
Discussion
This subroutine allows you to set the value of one or more bits in a byte while leaving others unchanged.
Effectively, the result is the same as using the statement below.
target = (target And Not mask) Or (value And mask)
The mask parameter governs which bits will get updated. For each bit of the mask parameter that is a 1,
the corresponding bit of the target will be set to the state of the corresponding bit of the value
parameter. Bits of the target that correspond to zero bits of the mask parameter will remain
unchanged.
The advantage to using the SetBits() subroutine instead of the equivalent statement is twofold. Firstly,
it is more efficient, resulting in less code and faster execution time. Secondly, and perhaps more
importantly, it performs the action as an atomic operation, i.e. one that is guaranteed, once begun, to
complete without an intervening task switch. This characteristic makes SetBits() useful for modifying
I/O ports and other Byte values in a multi-tasking environment.
Example
' set the middle 4 bits of Port C to the binary value &B0110
Call SetBits(Register.PortC, &H3C, &H18)
Compatibility
This routine is not available in BasicX compatibility mode. Also, it is only supported by ZX firmware later
than v1.0.0.
See Also
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