Practical_modern_SCADA_protocols_-_dnp3,_60870-5_and_Related_Systems

476 Practical Modern SCADA Protocols: DNP3, 60870.5 and Related Systems
Interpretation:
Case
Interpretation
F=, E= Value =
F non-zero, E=
Non-normalised number Value = (-1) S x 2 E-126 x (0.F)
F non-zero, E Normalised number Value = (-1) S x 2 E-127 x (1.F)
F=, E=
Value = (-1) S x infinity
F non-zero, E= Not a valid number
Note that a normalised number is one in which has been scaled to the form 0.1xxxx so that
it falls between 0.1 and 1.0, and then multiplied by 2 to give 1.xxxx. This removes the
leading ‘1’ to the right of the radix point, which is redundant because it is always a 1.
BCR
Binary counter reading
7 6 5 4 3 2 1 0
Octet 1 7 0
Octet 2 15 8
Octet 3 23
Counter I32
16
Octet 4 31 24
Octet 5 IV CA CY SQ
Key
I32 Counter value I32[0..31]
SQ Sequence number UI5[32..36]
CY Carry
CA Counter adjusted
IV Counter valid
SCO
Single command
This is a command to operate a single output. Bits 2 to 7 are the Qualifier of Command
sub-field. This is used for other commands also.