Literal values

Literal values of MATRIX variables can be expressed in BNF syntax as follows:

 matrix_literal ::= '[' [vector_literal {',' vector_literal}] ']

 vector_literal ::=    '[' [float_value {',' float_value}] ']'

The syntax of float_value is any string accepted by the java.lang.Float.valueOf(String) method.

Each vector_literal element represents a row of the matrix; for instance, the literal [[1,2],[3,4]] represents the matrix

 1.0 2.0 
 3.0 4.0 

Missing elements are assigned zero values; for instance, the literal [[],[1,2],[3,4,5]] represents the matrix

 0.0 0.0 0.0 
 1.0 2.0 0.0 
 3.0 4.0 5.0 

For examples of the use of MATRIX literals, see the MATRIX_DEMO and M_OPS_DEMO system configurations.

ASN.1 Encoding

MATRIX data is transferred according to the following modified ASN.1 syntax:

 MATRIX ::= [PRIVATE 3] IMPLICIT SEQUENCE {
     rows IMPLICIT USINT,
     cols IMPLICIT USINT,
     IMPLICIT SEQUENCE OF IMPLICIT REAL}

The encoding of MATRIX elements is constructed in the sense of ISO/IEC 8825, with the following extensions to the COMPACT encoding described in Annex E of IEC 61499-1:

1. rows and cols, representing the number of rows and columns in the matrix respectively, are encoded as values of the USINT type without identifier or length octets, i.e., as two successive 8-bit unsigned integers.
   • This restricts the maximum number of elements of a MATRIX to 65025 (255×255).
   • If the matrix data is to be transferred via PUBLISH/SUBSCRIBE, the maximum number of elements is further restricted by the maximum number of octets (1472) that can be transferred in a single UDP packet without segmentation; otherwise, an OVERFLOW error will be declared by the corresponding FB instance.
   • Since the encoding of a REAL value requires 32 bits (4 octets), the maximum number of elements in a MATRIX instance to be transmitted via PUBLISH/SUBSCRIBE would then be (maximum octets - tag octets - length octets)/(element length) = (1472-1-2)/4 = 367 elements. For instance, a square matrix with 19 rows and columns, containing 361 elements, would fit in a UDP packet.
   • MATRIX data larger than the allowed UDP transfer should be transferred using the CLIENT/SERVER mechanism.
2. The matrix contents are encoded using the COMPACT syntax for an ARRAY of IEC 61131-3 REAL values, without any tag or length subfields.
3. Data is encoded in column order; for instance, the matrix
   

    0.0 0.0 0.0 
    1.0 2.0 0.0 
    3.0 4.0 5.0 

   
   would be encoded in the order
   

   (0.0,1.0,3.0,0.0,2.0,4.0,0.0,0.0,5.0)

For an example of the application of these encoding rules, see the CODEC_TEST2 system configuration.