Types Of Blocks; Figure 1: Conditional Block Call - GE PACSystems RX7i Cpu Programmer's Reference Manual

Chapter 2. Program Organization
2.1.5

Types of Blocks

PACSystems supports four types of blocks.
Block Type Local Data
Has its own local
Block
data
Parameterized Inherits local data
Block from caller
User Defined
Has its own local
Function Block
data
(UDFB)
Inherits local data
External Block
from caller
All PACSystems block types automatically provide an OK output parameter. The name used to
reference the OK parameter within a block is Y0. Logic within the block can read and write the Y0
parameter. When a block is called, its Y0 parameter is automatically initialized to TRUE. This will
result in a positive power flow out of the block call instruction when the block completes execution,
unless Y0 is set to FALSE within the logic of the block.
For all block types, the maximum number of input parameters is one less than the maximum number
of output parameters. This is because the EN input to the block call is not considered to be an input
parameter to the block. It is used in LD language to determine whether or not to call the block, but is
not passed into the block if the block is called.
Program Blocks
Any block can be a program block. The _MAIN block is automatically declared when you create a
block-structured program. When you declare any other block, you must assign it a unique block
name. A block is automatically configured with no input parameters and one output parameter (OK).
When a block-structured program is executed, the _MAIN block is automatically executed. Other
blocks execute when called from the program logic in the _MAIN block, another block, or itself. In the
following example, if %M00001 is ON, the block named ProcessEGD will be executed:
Program Blocks and Local Data
Program blocks support the use of %P global data. In addition, each block, except _MAIN, has its own
%L local data. Blocks do not inherit %L local data from their callers.
8 PACSystems* RX7i, RX3i and RSTi-EP CPU Programmer's Reference Manual
Programming
Size Limit
Languages
LD
FBD 128 KB
ST
LD
FBD 128 KB
ST
LD
FBD 128 KB
ST
user memory
C size limit (10
MB)

Figure 1: Conditional Block Call

Parameters
0 inputs
1 output
63 inputs
64 outputs
63 inputs
64 outputs
Unlimited internal member
variables
63 inputs
64 outputs
GFK-2950C