Micromod MOD: 1800P - MOD 30ML Identity Module (Version 2) Algorithms, Tables and Sequential Logic Functions - Manual (Page 153)

Logic Functions - Book 2
CONFIGURING THE SEQUENCE BLOCK
11-7
Defining the Steps
The sequence for this application requires six steps as described in Section 11.2.1. These
steps can be named as follows:
Step 1 Idle Step 3 Heat Step 5 Cool
Step 2 Fill Step 4 Cook Step 6 Drain
The output state for each of the three outputs must be defined for each step. For example, in
the Idle step, the fill valve (Output 1) and drain valve (Output 2) must both be shut (False).
The output requirements for each step in the sequence are shown in Table 11-5.
Table 11-5. Output Requirements for Each Step
Step No. Step Name Output No 1
Fill Valve
Output No 2
Drain Valve
Output No 3
Setpoint
1 Idle False False 100
2 Fill True False 100
3 Heat False False 250
4 Cook False False 250
5 Cool False False 100
6 Drain False True 100
The transition logic makes the sequence change from one step to another. The logic is
defined by transition expressions which are written by the user. See Section 10.4.4
Transition Expressions for a description of transition expressions and a listing of the
operators.
The Sequence Block functions very much like a drum stepper. It can also perform the same
type of sequencing done in Ladder Logic. Unlike these, there is no requirement to progress
sequentially through each step one after the other. The IF-THEN-ELSE statements used in
transition expressions allow skipping of steps, naming of steps for various conditions, and
return to previous steps. Also, the transition logic can combine any of the data types used
within MODCELL. For example, a transition expression can specify:
If digital Input 1 is true,
and the time in step exceeds 2 hours and 25 minutes, and the temperature is 348 degrees
Celsius, then go to Step 6, otherwise go to Step 4.
Since the purpose of this example is only to demonstrate the method of configuring the
Sequence Bock, the transition logic is fairly basic and progression through the steps is
sequential. Define the steps, output states and transition logic using the step-by-step
instructions in Table 11-6.