Micromod MOD: 1800P - MOD 30ML Identity Module (Version 2) System, I/O and Communications Functions - Manual (Page 15)

Logic Functions - Book 1
DATABASE DESCRIPTION
2-3
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Function blocks
Process input function blocks configure an interface between the instrument’s process
input module blocks and the control tasks. Algorithm function blocks define the user
configured control functions on the instrument. These building blocks include
expressions, linearization, notification messages, piecewise tables, process alarms, timers
and sequencers. Communication function blocks support the instrument communication
ports, and the transfer of data over them. The configured list block handles transfer of
data between groups, as well as transfer of data to the communication interfaces.
Block Parameters
Blocks are comprised of attributes, with each attribute containing a value of a specific type
such as floating point, discrete, state, and time (see Section 2.3.2 for data types). Some of
these attributes are internal to the block (not visible to the user through configuration), and
contain values processed during block execution; other attributes are accessible through
configuration. Some attributes are uniquely defined in the database and are therefore
addressable by name, coupled with the block type and occurrence number. This reference to
an attribute is called a Logical Source Pointer (LSP). Attributes can be input sources or
values, calculated output values, and parameters for specific execution of the block. For
example, the LSP to the Timer Block 1 time value would be constructed as TM1,TIME.
An input attribute provides data that is used by the block. Input data may be specified as a
local value, a remote pointer to a block attribute from which the input value is obtained, or
NONE, in which case this particular input is not used by this occurrence of the block. An
input, which specifies a block attribute as the source of its value, is referred to as a "logical
source pointer."
An output attribute contains a value produced as a result of the execution of the block. For
example, a block might produce a discrete value of TRUE or FALSE depending on the result
of a comparison of its inputs. This attribute can then be used as an input to another block.
Output attributes are always immediately followed by a data quality attribute. Data quality is
set to good if a valid output value has been produced. If an error occurred during the
execution of the block, or if block inputs had bad quality, the data quality attribute will be set to
a value indicating that the output value has bad quality. The quality attribute can be used by
other blocks, which use this block’s output as their input source, in order to determine whether
or not the value should be used.
Other attributes are configuration parameters which are not specifically inputs or outputs, but
effect the action taken by the block. For example, a block may have attributes to enable the
main function or sub functions, cause it to invert its normal output value, perform increment or
decrement operations, contain target or default values, and so forth.
2.2.2 Loops
All user configurable function blocks are placed into groups in the database preceded by loop
blocks. The reasons for this grouping of function blocks are:
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Control access of the instrument by computer or console sources is at this group level.
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All blocks in this group are executed at a rate specified for the loop block.
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Execution of this entire group can be turned off and on via an attribute in the loop block.