Bit Shift Right (BSR)
The BSR instruction shifts the specified bits within the Array one position right. When enabled, the instruction unloads the value at bit 0 of Array to the .UL bit, shifts the remaining bits one position right, and loads the bit from the Bit address.
IMPORTANT:
Test and confirm that the instruction changed the correct data. The BSR instruction operates on continuous memory. If an Array is a member array, the instruction may shift beyond the boundary of the array into other members following it. Be sure to carefully select a length that does cause this scenario to occur.
The BSR instruction operates on contiguous data memory.
If the instruction tries to read past the end of an array (the LEN is too big), the instruction sets the .ER bit and generates a major fault.
Available Languages
Ladder Diagram
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Operands
There are data conversion rules for mixed data types within an instruction. See Data Conversion.
Ladder Diagram
Operand | Data Type | Format | Description |
|---|---|---|---|
Array | DINT ARRAY | tag | Array to modify specify the first element to be shifted. |
Control | CONTROL | tag | Control structure for the operation |
Source Bit | BOOL | tag | Bit to load into the vacated position. |
Length | DINT | immediate | Number of bits in the array to shift |
CONTROL Structure
Mnemonic | Data Type | Description |
|---|---|---|
.EN | BOOL | The enable bit indicates the BSR instruction is enabled. |
.DN | BOOL | The done bit is set to indicate that bits shifted one position to the right. |
.UL | BOOL | The unload bit is the instruction’s output. The .UL bit stores the status of the bit that was shifted out of the range of bits. |
.ER | BOOL | The error bit is set when .LEN < 0. |
.LEN | DINT | The length specifies the number of array bits to shift. |
Affects Math Status Flags
No
Major/Minor Faults
None specific to this instruction. See Index through arrays for array-indexing faults.
Execution
Ladder Diagram
Condition/State | Action Taken |
|---|---|
Prescan | The .EN bit is cleared to false. The .DN bit is cleared to false. The .ER bit is cleared to false. The .POS value is cleared. |
Rung-condition-in is false | The .EN bit is cleared to false. The .DN bit is cleared to false. The .ER bit is cleared to false. The .POS value is cleared. |
Rung-condition-in is true | See the following BSR Flow Chart (True) |
Postscan | N/A |
BSR Flow Chart (True)
Examples
Example 1
When enabled, the BSR instruction copies array_dint[0].0 to the .UL bit, shifts 0-9 to the right, and loads the input_1 into array_dint[0].9. The remaining bits (10-31) are invalid, which indicates the bits may not be modified.
Ladder Diagram
Example 2
When enabled, the BSR instruction copies array_dint[0].0 to the .UL bit, shifts 0-9 to the right, and loads the input_1 into array_dint[1].25.. The remaining bits (31-26 in dint_array[1]) are invalid, which indicates that the bits may not be modified. Note how array_dint[1].0 shifts across words into array_dint[0].31.
Ladder Diagram
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