Bit Shift Right (BSR)
This table lists the controllers and applications that support this instruction.
Architecture | Standard applications | Safety applications |
|---|---|---|
CompactLogix 5370, ControlLogix 5570, Compact GuardLogix 5370, and GuardLogix 5570 controllers | Yes | No |
CompactLogix 5380, ControlLogix 5580, Compact GuardLogix 5380, GuardLogix 5580, and
ControlLogix 5590 controllers | Yes | Yes |
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
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
Fault conditions
This table lists a major fault specific to the BSR instruction.
Error code | Type | Description |
|---|---|---|
20 | 4 | A major fault occurs if the first specified bit plus the number of bits to be
shifted passes the end of the array. |
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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