Micromod MOD: 1800P - MOD 30ML Identity Module (Version 2) System, I/O and Communications Functions - Manual (Page 13)

Logic Functions - Book 1
DATABASE DESCRIPTION
2-1
2
DATABASE DESCRIPTION
2.1 GENERAL
This section describes the structures and global features that support the instrument database
and it describes general instrument operation and how the database is protected.
Understanding the basic elements that support database creation and operation is
fundamental in knowing how the configuration will affect instrument performance. How
individual parameters affect the function of the instrument during database execution is
described in the next section. Since commonality exists in certain basic functions, this section
is used as a common reference point to describe these global features.
2.2 DATABASE STRUCTURE OVERVIEW
The user database is configurable and writable to make the instrument perform a variety of
executable functions. The basic logical element of the database is a function block. Function
blocks are grouped to form multiple process loops. The significance of a loop is that it is at
this level that control access by an external computer or console can be obtained. Loops in
turn are grouped into a set of loops that are scanned (executed) at the same rate. Up to five
different scan rates can be configured through the interface block. The instrument operates at
a fixed base rate (50 milliseconds) and each of the five groups can be configured at any
multiple of the base rate up to the maximum time value (about 1193 hours). Module blocks
define the physical interface to the database and serve as data handling blocks between the
process and the function blocks. Figure 2-1 shows the relationship between the basic
configurable elements of the instrument database.
2.2.1 Blocks
Blocks perform specific activities or algorithms based on their type. Each type of block within
the instrument is uniquely defined by an occurrence number (the number of the instance of a
block type in the database).
Blocks are comprised of attributes, which specify block input values or sources, block output
values calculated as a result of performing some specified activity, and other parameters
which affect the function of a block.
Features of blocks include:
•
Data quality associated with pertinent block attributes (typically, block outputs).
•
Selection of either a local data value or a Logical Source Pointer (LSP) connection to a
block attribute for any block input.
•
Support of indirect input source connections (for example, a block may have specified as
its input an attribute of another block which in turn specifies an attribute from yet another
block as its input source).
•
A block state attribute that allows certain blocks to be "turned off," or kept from executing
and updating its outputs.