Description
You use the "Reset bit field" instruction to reset several bits starting from a certain address.
You specify the number of bits to be reset with the value of the constant at the N input. The address of the first bit to be reset is defined by <Operand>. If the value of the constant may not be greater than the number of bits in a selected byte. If this value is greater, the instruction is not executed and the error message "Range violation for index <Operand 1>" is displayed. The bits remain set until they are explicitly reset by another instruction.
The instruction is only executed if the enable input EN has the signal state "1".
Bit fields of the type PLC data type, STRUCT or ARRAY
With structures of the type PLC data type, STRUCT or ARRAY, the number of bits contained in the structure represents the maximum number of bits that can be set:
-
If you specify the value "20" at the N input, for example, and the structure only contains 10 bits, then only these 10 bits are reset.
-
If you specify the value "5" at the N input, for example and the structure contains 10 bits, then exactly 5 bits are reset.
Parameters
The following table shows the parameters of the "Reset bit field" instruction:
|
Parameters |
Declaration |
Data type |
Memory area |
Description |
|
|---|---|---|---|---|---|
|
S7-1200 |
S7-1500 |
||||
|
EN |
Input |
BOOL |
I, Q, M, D, L or constant |
I, Q, M, D, L, T, C or constant |
Enable input |
|
N |
Input |
UINT |
Constant |
Constant |
Number of bits to be reset |
|
<Operand> |
Output |
BOOL |
I, Q, M With a DB or an IDB, an element of an ARRAY[..] of BOOL |
I, Q, M With a DB or an IDB, an element of an ARRAY[..] of BOOL |
Pointer to the first bit to be reset. |
Example
The following example shows how the instruction works:
If the operands "TagIn_1" and "TagIn_2" have the signal state "1", 5 bits are reset starting at the address of the operand "MyDB".MyBoolArray[4].