# LGF_ShiftRegister (FB / V1.0.3)

Author: Siemens Digital Industry Support

## Short description

The Function represents a shift register for any kind of Datatype (using `variant`).
It is possible to shift the elements in the array at `bufferRegister` to the left (index `array[n]:=array[n+1]`) or right (index `array[n]:=array[n-1]`).
It could be used for material tracking trough a machine or a process, e.g. for a rotary indexing table.

Note
  As this is a real shift operation, it may cause some runtime effects while using big array sizes to move at the input `bufferRegister`.
  Please consider that a FIFO or LIFO storage, based on indexes, could be used as well for most applications.

### Block Interface

| LGF_ShiftRegister (FB) |
--- | --- | ---
Bool |  |  | shiftLeft |  | error |  |  | Bool
Bool |  |  | shiftRight |  | status |  |  | Word
UInt |  |  | shiftRange |  | subFunctionStatus |  |  | Word
Bool |  |  | clear |  |  |  |  |
Bool |  |  | fill |  |  |  |  |
Variant |  |  | initialItem |  |  |  |  |
Variant |  |  | bufferRegister |  |  | Variant

### Input parameter

Identifier | Data type | Default value | Description
--- | --- | --- | ---
shiftLeft | Bool | FALSE | Rising edge: Elements in the array `bufferRegister` shifted left. Elements moved from index `N` to `N - 1`. The element at index `N = 0`is overwritten
shiftRight | Bool | FALSE | Rising edge: Elements in the array `bufferRegister` shifted right. Elements moved from index `N` to `N + 1`. The element at index `N = lastIndex` is overwritten
shiftRange | UInt | 1 | Number of places to be shifted in the `bufferRegister` input array
clear | Bool | FALSE | Clear buffer elements in `bufferRegister` with `initalItem`
fill | Bool | FALSE | Overwrite buffer elements after shift operation. * `shiftLeft` - the most right element/s * `shiftRight` - the most left element/s overwritten by `initalItem`.
initialItem | Variant | --- | Value with which the array at input `bufferRegister` is initialized (usually the default value)

### Output parameter

Identifier | Data type | Description
--- | --- | ---
error | Bool | FALSE: No error TRUE: An error occurred during the execution of the FB
status | Word | 16#0000-16#7FFF: Status of the FB 16#8000-16#FFFF: Error identification (see following Table)
subFunctionStatus | Word | Status or return value of called FB's, FC's and system blocks

### In/Out parameter

Identifier | Data type | Description
--- | --- | ---
bufferRegister | Variant | Buffer / Register memory as ARRAY, which keeps the data. The data in the register is shifted left or right depending on the command.

### Status & Error codes

Code / Value | Identifier / Description
--- | ---
16#0000 | STATUS_NO_ERROR Status: Execution finished without errors
16#7000 | STATUS_NO_CURRENT_JOBS Status: No current jobs, initial state
16#8200 | ERR_NO_ARRAY Error: No array is present at the input `bufferRegister`
16#8201 | ERR_CLEARING_WITHOUT_INITIAL_ITEM Error: Claering `bufferRegister` without an `initialItem` is not possible.
16#8202 | ERR_FILL_WITHOUT_INITIAL_ITEM Error: Option `fill` the buffer after shift operation without an `initialItem` is not possible.
16#8203 | ERR_WRONG_TYPE_INITIAL_ITEM Error: The data type of the input `initialItem` does not correspond to the data type of the array at the InOut parameter `bufferRegister`.
16#8401 | ERR_MORE_THAN_ONE_COMMAND Error: More than one command present at the same time. Only one of the inputs `shiftLeft`, `shiftRight` or `clear` is allowed.
16#8402 | ERR_IN_SHIFT_RANGE Error: The value at `shiftRange` must not exceed the maximum size of the Array at `bufferRegister`.
16#8610 | ERR_CLEAR_BUFFER Error: While clearing buffer in block `MOVE_BLK_VARIANT``. Check `subFunctionStatus` code.
16#8611 | ERR_SHIFT_BUFFER_LEFT Error: While shift buffer left in block `MOVE_BLK_VARIANT` - check `subFunctionStatus` code
16#8612 | ERR_SHIFT_BUFFER_LEFT_FILL Error: While fill buffer after shift left in block `MOVE_BLK_VARIANT` - check `subFunctionStatus` code
16#8622 | ERR_SHIFT_BUFFER_RIGHT Error: While shift buffer right in block `MOVE_BLK_VARIANT` - check `subFunctionStatus` code
16#8622 | ERR_SHIFT_BUFFER_RIGHT_FILL Error: While fill buffer after shift right in block `MOVE_BLK_VARIANT` - check `subFunctionStatus` code

## Change log

Version & Date | Change description
--- | ---
| 01.00.00 | Siemens Industry Online Support
| 03.07.2018 | First released version
| 03.00.00 | Simatic Systems Support
| 09.04.2021 | Refactoring and alignment to Datatype Variant Insert documentation