Rockwell Automation 1336T Function Block Prog. Manual, Series A/B - Manual (Page 35)

Chapter 2
2–1
1336 FORCE — 5.9 August 1995
System Component Detail
This chapter provides information about the following system
component concepts:
❒
Execution lists and their events
❒ Downloading and compiling function block applications
❒
Understanding function block I/O nodes
❒
Connecting or linking blocks
An execution list provides a way for you to organize the function
blocks, or events, in the order that you want the drive to execute the
events. Within an execution list, you may have up to 128 events in
any combination. Each event is defined by a block type number and
a block ID number.
❒
The block type number specifies one of the 28 function types to
create and execute. Chapter 4 provides information about the
available function types.
❒
The block ID identifies each event as being unique. The block ID
does not indicate when the event will be executed. Instead, the
drive uses the block ID to differentiate one event from another
event with the same block type number. The block ID must be
between 1 and 254.
For example, you could have an event that has a block type number
of 8, which would specify a FILTER function block, and a block ID of
12. If you include a second FILTER function block with different
input parameters, the second entry requires a new block ID; such as
27. By doing this, the compiler can distinguish between the FILTER
function blocks, even if you later change the position of the events
within the execution list.
Once a block ID is assigned to a certain event with a specific type,
that ID number cannot be used again within the same list with a
different type number. In the same execution list, you could not
assign a block ID of 12 to an event with a block type of 20
(specifying a SCALE function).
The position of each event in the execution list implies an associated
execution sequence number. The execution number specifies the
order in which the event is to be executed. When you use a PLC, the
execution numbers are not visible, but the events are executed in the
order that they are listed in the PLC data table.
Chapter Objectives
Execution List Overview