FC 124 - Sequence Monitor

The sequence monitor function code controls the execution of a sequence generator block by selecting the order of step execution in a process based on system and external inputs. The sequence monitor block performs a logic action based on the value of the control status input from a device monitor block and a boolean step trigger input. Depending on the value of the control status input, the next step can be a fault step or a normal step determined by internal logic. The sequence monitor block can be placed in either automatic or semi-automatic mode, and includes hold/initialize and executed stop (ESTOP) inputs. Each sequence monitor block handles up to eight steps. If more than eight steps are required, a number of sequence monitor blocks can be chained together in series fashion with S1. The sequence monitor block defines step type, next step, and fault values for each step.

 

Outputs:

Blk

Type

Description

N

R

Jump step number

N+1

B

Jump step trigger

 

 

Specifications:

Spec

Tune

Default

Type

Range

Description

S1

N

0

I

Note 1

Block address of next sequence monitor block associated

with this sequence of steps:

0 = no more blocks

S2

N

5

I

Note 1

Block address of control status input

S3

N

0

I

Note 1

Block address of step trigger

S4

N

0

I

Note 1

Block address of hold/initialize input (hold current step on 0 to 1 transition of input)

S5

N

0

I

Note 1

Block address of semi-automatic trigger (initiate next step on a 0 to 1 transition of input)

S6

N

0

I

Note 1

Block address of E-STOP input (block will be reset to Step 0 when <S6>=1)

S7

N

5

I

Note 1

Block address of initial step number (reset step)

S8

Y

1

I

Note 1

Block address of semi-automatic permissive:

<S8> = 0 = semi-automatic mode allowed

<S8> = 1 = semi-automatic mode not allowed

S9

Y

0

I

0 - 22

Step 1 type:

0X = permit hold and semi-automatic modes

1X = permit hold only

2X = permit no option

X0 = advance when <S2> = 0.0 and <S3> = 1only

X1 = advance when <S2> = 0.0

X2 = advance when <S3> = 1 only

S10

Y

0

I

0 - 22

Step 2 type

S11

Y

0

I

0 - 22

Step 3 type

S12

Y

0

I

0 - 22

Step 4 type

S13

Y

0

I

0 - 22

Step 5 type

S14

Y

0

I

0 - 22

Step 6 type

S15

Y

0

I

0 - 22

Step 7 type

S16

Y

0

I

0 - 22

Step 8 type

S17

Y

0.000

R

Full

Step to execute after Step 1 if input is good

S18

Y

0.000

R

Full

Step to execute after Step 2 if input is good

S19

Y

0.000

R

Full

Step to execute after Step 3 if input is good

S20

Y

0.000

R

Full

Step to execute after Step 4 if input is good

S21

Y

0.000

R

Full

Step to execute after Step 5 if input is good

S22

Y

0.000

R

Full

Step to execute after Step 6 if input is good

S23

Y

0.000

R

Full

Step to execute after Step 7 if input is good

S24

Y

0.000

R

Full

Step to execute after Step 8 if input is good

S25

Y

0.000

R

Full

Step 1 fault step (control status input bad)

S26

Y

0.000

R

Full

Step 2 fault step (control status input bad)

S27

Y

0.000

R

Full

Step 3 fault step (control status input bad)

S28

Y

0.000

R

Full

Step 4 fault step (control status input bad)

S29

Y

0.000

R

Full

Step 5 fault step (control status input bad)

S30

Y

0.000

R

Full

Step 6 fault step (control status input bad)

S31

Y

0.000

R

Full

Step 7 fault step (control status input bad)

S32

Y

0.000

R

Full

Step 8 fault step (control status input bad)

 

NOTES:

1. Maximum values are: 9,998 for the BRC-100, IMMFP11/12 and 31,998 for the HAC

 

 

124.1  Explanation

 

The sequence monitor block uses the values of two inputs to determine the next step number in a batch process. The first input is the control status input read from a device monitor block. This input defines the current state of the devices that the sequence generator block controls. This input can be 0.0 (good), 1.0 (bad), or 2.0 (waiting). If even one device is bad, this input is marked bad (value equals 1.0). The second input is the step trigger. The step trigger is dependent on the current step and the results of auxiliary logic associated with the device in question.

 

Each step of a batch sequence often requires auxiliary logic to perform functions in addition to activating/deactivating discrete devices (i.e., change controller set points, totalize flow, etc.).

Figure 124-1 shows how this auxiliary logic ties into the batch execution configuration. The auxiliary logic executes according to the current step number read from the sequence generator block. The current step number input then selects from the results of that auxiliary logic the boolean signal that will be output to the sequence monitor block as the step trigger.

 

 

The values of the step trigger and the control status input are tested against several operator defined parameters to determine which step executes next.

 

The sequence monitor block has both a next step and a fault step for each step number. When the control status input is bad (1.0), this function automatically selects the fault step number. The fault step number goes to the sequence generator block if the step type requires a good status input to continue with the sequence. If the control status input is good (0.0), or waiting (2.0), the output depends on the step type defined in the specification descriptions.

 

The sequence monitor block can operate in either an automatic or semi-automatic mode. In the automatic mode, the sequence is dependent on the values of the control status input and the step trigger. In the semi-automatic mode, the sequence is dependent on the values of the control status input, the step trigger, and the semi-automatic step trigger. The operator must activate the semi-automatic step trigger manually to proceed with the sequence as one of the conditions to go to the next step. The block can be placed in semi-automatic mode only if both the semi-automatic permissive and step type specifications permit it.

 

NOTE: For the sequence monitor to begin execution from Step 0, the old/initialize input <S4> must toggle from one to zero while the value of <S7> dictates the beginning step number to execute.

 

 

124.1.1  Specifications

 

S1 - NXT

Block address of next sequence monitor block in the series of blocks used to execute the sequence. If this value equals zero, there are no more blocks in the sequence. Each sequence monitor block can accommodate eight steps of a sequence. If the sequence contains more than eight steps, sequence monitor blocks can be linked in a series, with the last step of the first block initializing the first step of the next block, etc. Therefore, Steps 1 through 8 in the second sequence monitor block are Steps 9 through 16 in the sequence.

 

S2 - CSI

Block address of control status input (typically a device monitor block). The value in this block represents the control status of all the devices in the control loop. The output of this block is good when all the inputs are good, bad when any one input is bad, and waiting if any input is waiting for a reply from a device driver block and no inputs are bad. This value and the value of the step trigger are used to select the next step in the sequence. When the control status input is bad, the fault value for the next step is automatically output if the step type is one that requires a good status to continue with the

sequence. If the control status input is good or waiting, output depends on the step type (S9) for the current step.

0.0 = good

1.0 = bad

2.0 = waiting

 

NOTE: Any step trigger (S3) or semi-automatic mode trigger (S5) that occurs while the control status input is 2.0 (waiting) is remembered and therefore acted upon when the control status input becomes 0.0 (good).

 

S3 - STEP

Block address of step trigger. The value in this block, used with the control status input, selects the next step in the control sequence. Auxiliary logic used for the batch process generates the step trigger. The sequence monitor recognizes the trigger when it goes from a zero to one state and when it is held high in its one state.

 

S4 - HOLD

Block address of hold/initialize value. The sequence monitor block can hold the sequence at certain steps. The hold/initialize function is active only when the step type specification is configured to permit it.

1 = the sequence holds at the current step.

1 to 0 transition = the sequence monitor block begins execution with the initial step specified by S7.

0 = sequence is in run mode.

 

NOTE: To enable the sequence monitor to resume running from the current step after the hold, it is necessary to feed the jump step number output N into input S7.

 

S5 - SEMI

Block address of semi-automatic mode trigger. When the semi-automatic mode is permitted by step type (S9) and the semi auto permissive (S8), the operator must change this value from zero to one as one of the conditions for initiation of the next step of the sequence.

 

S6 - E-STOP

Block address of E-STOP (executed stop) input. The E-STOP specification drives the sequence to Step 0 (the reset step) whenever it has a value of one. The block referenced by this specification is normally a remote control memory function block used as an E-STOP. Thus, reserve the disable mask (Step 0) in sequence generator blocks driven by the sequence monitor block for E-STOP.

 

S7 - INIT

Block address of initial step number. When the block is initialized by a one to zero transition of <S4>, the sequence begins with the step identified in this block.

 

S8 - PERM

Block address of the semi-automatic permissive. When the value in the block is a zero, the semi-automatic mode is permitted unless step type (S9) overrides it.

<S8> = 0, semi-automatic mode permitted.

<S8> = 1, automatic mode permitted.

 

S9 - TYPE1

Step 1 type. Each step type is made up of two digits. The ones digit defines the states of the control status input and step

trigger necessary for the block to initiate the next step of the sequence. The tens digit identifies the control options available

to the operator for the step.

 

                                         

S10 to S16 - TYPE2 to TYPE8

Step types for Steps 2 through 8 defined in S9.

 

S17 to S24 - STEP1 to STEP8

Define the number of the step the system should execute after Step n (n equals one to eight) is completed when the block

is operating normally.

 

S25 to S32 - FAULT1 to FAULT8

Define the number of the fault step the system should execute after Step n (n equals one to eight) is completed when the

block receives a bad (1.0) input from the device monitor block and step type requires a good control status input.

 

124.1.2   Outputs

 

N

(Jump step number) Identifies the number of the step performed at the conclusion of the current step.

 

N+1

(Jump step trigger) Upon a zero to one transition of output N+1, initiates a step jump in the sequence generator block.

The sequence generator block then executes the step identified by the jump step number. A zero to one transition of this

value occurs when the sequence monitor block proceeds to the next step in the sequence (when the conditions defined by

the step type specification are met). This output makes a one to zero transition one segment cycle after the zero to one

transition.

 

 

124.2   Applications

 

Refer to function code 123 for an example of the sequence monitor block used in a batch process. Sequence monitor blocks can also be used for sequential control.