Rockwell Automation D64046.5.1 U MNL WIN DDMC - Manual (Page 17)

Chapter 1
Understanding How a DDMC32 System Works
1-5
For example, in the figure below, the expected input conditions for step 1
are (in order): off, off, off, off, don’t care. The instruction will enter this
step only when inputs 0, 1, 2, and 3 are off. This figure shows another
example of the SDS instruction looking for a step to enter.
SDS Instruction Looking for a Step to Enter
ACTUAL INPUTS
OFF
ON
OFF
ON
STEP 1 EXPECTED INPUTS STEP 2 EXPECTED INPUTS
When transition conditions are
used the instruction looks for a
match of actual and expected
inputs. If inputs do not match,
the instruction continues its
search.
When the instruction
finds a match, it enters
the step.
OFF
OFF
OFF
ON OFF
ON
OFF
ON ––> ON
––> ON
––> ON
––> OFF ––> ON
––> OFF
––> ON
––> OFF
During runtime, an input change or a step timer timeout directs the SDS to
another step. If the instruction detects a mismatch (the actual inputs do not
match the expected inputs), it generates a mismatch fault. To aid you with
programming, the software looks for obvious programmed mismatches
before you accept an instruction.
How the Combinatorial SDS Instruction Handles Inputs
Combinatorial equations define destination steps based on input state
values and the relationship between a collection of inputs. The
combinatorial equation lets you accommodate complex combinations in
the instruction while keeping the number of steps within a configuration to
a minimum. (You can define up to 4 logical AND combinations in an
8-input SDS instruction; You can define up to 8 ANDed conditions in a
16- or 32-input instruction.)