FIFO

 Function Block A function block groups an algorithm and a set of private data. It has inputs and outputs. - Manages a first in / first out list.

Inputs

Inputs	Data Type	Range	Unit	Default	Description
@Tail	ANY				Value of the oldest pushed value. Updated after call.
Buf[]	ANY				Array for storing values.
IN	ANY				Value to be pushed.
POP	BOOL				Pop a new value on the rising edge The transition of a digital signal from low to high. AKA: positive edge..
PUSH	BOOL				Push a new value on the rising edge.
RST	BOOL				Reset New start of the microprocessor. the list.

Outputs

Outputs	Data Type	Range	Unit	Description
EMPTY	BOOL			TRUE if the list is empty.
OFLO	BOOL			TRUE if the overflow is on a PUSH command.
Count Internal count pulses, 1 pulse = 1/2^20turn.	DINT			Number of values in the list.
pRead	DINT			Index Zero pulse (zero signal) of a hardware pin such as digital input or feedback pin. in the buffer of the oldest pushed value.
pWrite	DINT			Index in the buffer of the next push position Position means a point in space which is described by different coordinates. Depending on the used system and transformation it can consist of a maximum of six dimensions (coordinates).This means three Cartesian coordinates in space and coordinates for the orientation. In ACS there can be even more than six coordinates. If the same position is described in different coordinate systems the values of the coordinates are different..

Remarks

• IN, @Tail, and Buf[] must have the same data type.
  • It cannot be a STRING.
• The @Tail argument specifies a variable filled with the oldest push value after the block is called.
• Values are stored in the Buf[] array.
  • Data is arranged as a roll An angular deviation from an ideal straight line motion, in which the positioning table rotates around its axis of travel as it translates along that axis. over buffer and is never shifted or reset.
  • Only read and write pointers and pushed values are updated.
  • The maximum size of the list is the dimension of the array.
• The first time an instance of the FIFO function A function calculates a result according to the current value of its inputs. A function has no internal data and is not linked to declared instances. block is called, that instance stores which array is passed to BUF[].
  • If a later call to the same instance passes a different array for the BUF[] argument, the call is considered invalid and no action is performed.
  • In this instance, the EMPTY output returns TRUE.

FBD Language Example

FFLD Language Example

• In the FFLD Language, the input rung is the PUSH input.
  • The output rung is the EMPTY output.

IL Language Example

(* MyFIFO is a declared instance of FIFO function block *)
Op1: CAL MyFIFO (PUSH, POP, RST, IN, @Tail , BUFF[])
FFLD  MyFIFO.EMPTY
ST Structured text - A high-level language that is block structured and syntactically resembles Pascal.  EMPTY
FFLD  MyFIFO.OFLO
ST  OFLO
FFLD  MyFIFO.COUNT
ST  COUNT
FFLD  MyFIFO.PREAD
ST  PREAD
FFLD  MyFIFO.PWRITE
ST  PWRITE

ST Language Example

(* MyFIFO is a declared instance of FIFO function block: *)
MyFIFO (PUSH, POP, RST, IN, @Tail , BUFFER);
EMPTY := MyFIFO.EMPTY;
OFLO := MyFIFO.OFLO;
COUNT := MyFIFO.COUNT;
PREAD := MyFIFO.PREAD;
PWRITE := MyFIFO.PWRITE;

See Also

LIFO