FC 161 - Sequence Generator

The sequence generator function code contains a series of masks that are stepped through on an event or time basis. The masks define the states of eight boolean outputs for each step.

 

In addition to the eight step masks, there is a default mask often called Step 0 or E-STOP (executed stop). If the block resets or jump to Step 0 executes, E-STOP is the output. E-STOP defines the state of the outputs. Sequential stepping in ascending numerical order, and jumping to specific step numbers are the two methods of event stepping.

 

If a sequence has more than eight steps, sequence generator blocks can link in series. If there are more than eight outputs per step, sequence generator blocks can be linked in parallel to provide the required number of outputs.

 

Unlike the other batch function blocks (123, 124, 129, etc.), the last sequence generator in the series is the output.

 

Outputs:

Blk

Type

Description

N

B

Output 1 of current step

N+1

B

Output 2 of current step

N+2

B

Output 3 of current step

N+3

B

Output 4 of current step

N+4

B

Output 5 of current step

N+5

B

Output 6 of current step

N+6

B

Output 7 of current step

N+7

B

Output 8 of current step

N+8

R

Currrent step number

N+9

R

Seconds remaining in current step

N+10

B

Step taken (lobic 0 to 1 transition)

 

 

Specifications:

Spec

Tune

Default

Type

Range

Description

S1

N

0

I

Note 1

Starting block address of previous sequence

generator in series (0 = first in series)

S2

N

0

I

Note 1

Block address of step trigger (0 to 1 transition)

S3

N

0

I

Note 1

Block address of step hold:

0 = release

1 = hold

S4

N

0

I

Note 1

Block address of step timer hold:

0 = release

1 = hold

S5

N

0

I

Note 1

Block address of reset trigger (0 to 1 transition)

S6

N

0

I

Note 1

Block address of step jump trigger (0 to 1 transition)

S7

N

5

I

Note 1

Block address of step jump number

S8

N

0

I

Note 1

Block address of output disable flag

S9

Y

0.000

R

Full

Disable mask

S10

Y

0.000

R

Full

Step 1 output mask

S11

Y

0.000

R

Full

Step 1 time in seconds

S12

Y

0.000

R

Full

Step 2 output mask

S13

Y

0.000

R

Full

Step 2 time in seconds

S14

Y

0.000

R

Full

Step 3 output mask

S15

Y

0.000

R

Full

Step 3 time in seconds

S16

Y

0.000

R

Full

Step 4 output mask

S17

Y

0.000

R

Full

Step 4 time in seconds

S18

Y

0.000

R

Full

Step 5 output mask

S19

Y

0.000

R

Full

Step 5 time in seconds

S20

Y

0.000

R

Full

Step 6 output mask

S21

Y

0.000

R

Full

Step 6 time in seconds

S22

Y

0.000

R

Full

Step 7 output mask

S23

Y

0.000

R

Full

Step 7 time in seconds

S24

Y

0.000

R

Full

Step 8 output mask

S25

Y

0.000

R

Full

Step 8 time in seconds

 

NOTES:

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

 

 

 

161.1   Explanation

 

The sequence generator block controls a batch process by providing outputs that define the operating states for each step in a process for all the devices used. Figure 161-1 illustrates a typical arrangement. A sequence monitor or multi-sequence monitor block monitors the process and selects the order in which the process steps execute. The step number then goes to the sequence generator block that outputs the values identified with that step. Any number of sequence generator blocks can be linked in series or parallel to provide the required number of outputs or steps.

 

 

 

Figure 161-2 illustrates a configuration with sequence generator blocks ganged in series and in parallel. Sequence generators in series increase the step range by factors of eight. In Figure 161-2, blocks 60, 71 and 82 are in series, providing 24 steps. Running parallel to this sequence is the block series 93, 104 and 115. The first sequence generator has the value of zero for S1, identifying it as the first block in the series, with outputs zero through eight. In the figure, blocks 60 and 93 are the first in the series. The second block in the series must be greater in number than the first. Blocks 71 and 104 are the second blocks in the series, they have values of 60 and 93, respectively, for S1. This shows that they are not the first blocks in the series. They have step outputs nine through 16. This series relationship continues until the maximum number of steps needed is reached.

 

 

 

Sequence generators in series monitor the step number and step taken outputs from the preceding sequence generator block. Therefore, the outputs of the last sequence generator in a series represent the outputs used to drive device driver blocks.

 

In batch control applications, it is necessary to run the outputs (step jump trigger and step jump number) from the lead sequence monitor block (function code 124) to all of the sequence generator blocks used by the sequence. In this way, all blocks will move from step to step in unison. Furthermore, when using a sequence monitor (function code 124) or multi-monitor block (function code 135), leave all step timers in the sequence generator blocks at the default (zero) value. Figure 161-3 shows an application not using sequence monitor or multi-sequence monitor blocks. When sequence monitor or multi-sequence monitor blocks are not used, all sequence generator blocks ganged together must reference the same reset, jump trigger, jump step number, and disable inputs. This will force the sequence generator blocks to work in unison. If the step timer is being used, a good technique is to take the step taken indicator and current step output from the last sequence generator block for the first eight outputs, and use them as the step trigger and step number inputs for the other sequence generator blocks used in the sequence. Set the step timers for outputs greater than eight to zero. This way, the first series chain of sequence generator blocks will be timer controlled, and will drive the remaining blocks in unison.

 

 

 

With series sequence generator blocks, the sequence generator block handling outputs one through eight must have a lower block address than the block for Steps 9 through 16. Likewise, the sequence generator block Steps 9 through 16 must have a lower block address than the one for Steps 17 through 24. This is true for all chained blocks.

 

Processing of inputs to sequence generator blocks is done in the following order: reset, disable, jump, step hold, next step, and time hold.

 

To define the output masks, the operator enters a real value that internally converts to binary digits. The operator defines the output values needed for a given step, then converts them to a real number as shown in Table 161-2. The real number representing the desired output is the step mask for the desired step output.

 

 

 

161.1.1  Specifications

 

S1 - PREV

(Block address of previous sequence generator block in series) If the value equals zero, then the block is the first in the series. Each sequence generator block can output eight values for eight steps of a process. If more steps are required, the blocks can be ganged in series. If more than eight outputs are required, the blocks can be ganged in parallel.

 

S2 - STRIG

(Block address of step trigger) The value in this block controls sequence generator step execution when the sequence generator block is performing sequential stepping. On a zero to one transition of this input, the block will execute the step number which immediately follows the current step number.

 

S3 - HOLD

(Block address of step hold input) When this input is a one, and steps are being executed sequentially, the advance to the next step is disabled. When the input goes to zero, the next step will be executed. The step hold will not disable the step timer, but will prevent the block from executing the next step once the timer has expired. All blocks in series must have the same step hold input.

0 = execute next step

1 = hold

 

S4 - THOLD

(Block address of timer hold input) When this input is a one, the step timer is frozen at its current value. An input of zero will cause the timer to resume timing exactly where it left off. All blocks in series must have the same timer hold input.

0 = release

1 = hold

 

S5 - RESET

(Block address of reset trigger) On a zero to one transition of this input, the block will output the disable mask and reset to Step 0. All sequence generators ganged together in series or parallel must have the same reset input.

 

S6 - JMPTRG

(Block address of step jump trigger) When the value in the block indicated by this specification makes a zero to one transition, the step indicated by the step jump number (S7) will be executed.

 

S7 - JMPSTP

(Block address of the step to be executed when the jump step trigger makes a 0 to 1 transition) Jumping to a step number less than zero will cause a jump to Step 0 (same as reset). Jumping to a number higher than the highest step number available in the series chain will cause the highest available step number to be executed. All sequence generator blocks in a series or parallel chain must have the same jump step number and jump step trigger to operate in unison.

 

S8 - DISFLG

(Block address of output disable trigger) When this output is equal to one, it sets the outputs equal to the disable mask, but does not move the step number. If the steps are timed, the output disable trigger will hold the block at the current step and freeze the step timer. The output disable trigger does not disable step triggers; the block will still execute the sequence and advance the step number, but the output will be the disable mask. All sequence generators ganged together in series or parallel must have the same disable trigger.

 

S9 - DISMSK

(Disable mask) Real value which, when subjected to a binary conversion as shown in Table 161-1, provides safe outputs for all devices controlled by the sequence generator block. The disable mask is output in three situations: when the disable input is set, when the block is reset, and after all steps have been completed. In batch control, the disable mask is the same as Step 0 and is reserved as an E-STOP (executed stop).

 

S10, S12, S14, S16, S18, S20, S22 and S24

(Mask 1 through mask 8) Real values representing the output mask associated with Step 1 (mask one) through Step 8 (mask eight). The output mask is a series of binary digits defining the operating states for all devices associated with the sequence generator block. Refer to Table 161-1 for the definition of step inputs for sequence generator blocks.

 

S11, S13, S15, S17, S19, S21, S23 and S25

(Time 1 through time 8) Represents the time in seconds that it will take to run the step. The individual step timers start whenever the corresponding step is entered. If a step timer is enabled for a particular step, the sequence generator automatically advances to the next sequential step when the step timer expires. Step timers are disabled when less than or equal to zero. The timer hold and disable flags freeze the step timer. The step hold input does not freeze the step timer, but does disable the advance to the next step when the timer expires. When the step hold is removed, the block will advance to the next step. Adapting the value of a currently running step timer causes the timing to begin again at the adapted value.  Tuning any specification during an active step restarts the current step timer to its beginning value.

 

161.1.2  Outputs

 

N through N+7

Outputs (one through eight) of the current step. The output is a boolean value representing the operating state of the device controlled by the sequence generator block. All outputs should be read from the last sequence generator block in the series.

 

N+8

Current step number.

 

N+9

Time remaining in current step in seconds.

 

N+10

Step taken indicator. This output reflects whether the next step has been taken. A zero to one transition of this output indicates that the block has begun the next step in the sequence.

 

 

 

161.2   Applications

 

Refer to the applications section of function code 123 for an example of a sequence generator block used in batch control.