CHAPTER 4

Manufacturing Automation using PLCs

CHAPTER 7 RLL Design for Sequencing System

Chapter 7: RLL Design for Sequencing System

7.1 Commonly used industrial machine sequence.

7.2 Sequencing chart

7.3 Design Relay Ladder Logic for Sequencing Problems using PLCs.

7.3.1 Design RLL for Single-Path Machine Sequence Having Non-Sustain Control Signals

7.3.2 Design RLL for Single-Path Machine Sequence Having Sustain Control Signals

7.3.3 Design RLL for Multi-Path Sequencing Systems with Sustain Outputs

7.3.4 RLL for machine sequence with two or more alternative parallel paths

7.3.5 RLL for machine sequence with option of bypassing certain steps.

7.3.6 RLL for machine sequence with the option of repeating certain steps.

RLL Design, for Sequencing System

Most manufacturing process controls are based on sequencing control systems. Different techniques can be used to assist engineer to design the Relay Ladder Logic based on sequencing control technique. Sequencing charts, Cascade and Huffman methods techniques are examples, which can be used to design sequencing control systems. The two former techniques will be illustrated in this Chapter.

7.1 Commonly used industrial machine sequence

Sequencing control system can be considered as single path or multi-path systems. Multi-path or parallel path sequencing control system cover controlling multi-tasks in one time, while single task is considered for single-path sequencing system. Fig. 7.1 shows a sequencing machine systems commonly used by industry [7.1].

7.2 Sequencing chart

Sequence charts (also called time-motion diagrams, state diagram, or bar charts) are useful for visualizing the operation of switching systems. They can be used to describe the step-by-step operation of relay systems, pneumatic systems, or any other type of switching systems.

To illustrate how sequence charts are constructed, consider the Relay Ladder Logic given in Fig. 7.2. This relay ladder diagram used to actuate two double-acting pneumatic cylinders A and B, (see Fig. 7.2). 5/2 directional-control valves with solenoid and a return spring actuate each cylinder. The solenoids are labeled by A+ and B+, respectively, signifying that the cylinder moves in the + direction (i.e forward or extend position) whenever the solenoid is energized. Two limit switches, a+ and b+, are mounted to monitor when the respective cylinder reaches the extreme + position.

The sequencing chart corresponding to this system also is shown in Fig. 7.2. To construct this chart, we draw horizontal lines for each of the elements taking parts in the action, and vertical lines representing the different stages, or steps, in the systems sequence. The horizontal axis represents time, with no fixed time scale. Whenever a new event takes place, a new vertical line is allocated. These lines are labeled with Roman numbers, see Fig. 7.2 Thus the time between two adjacent vertical lines depends on when the events occur. Note, also that each cylinder is allocated two horizontal lines, to make it possible to represent cylinder motion between its two extreme positions. All other elements are preferably allocated only a single line. The time period during which a given element is actuated is indicated by a thick line stop (its horizontal line), with the beginning and end of actuation shown by short vertical lines. Machine sensors and actuators as well as the corresponding addresses used in PLC are listed below:

Machine sensors & operator control buttons

Addresses

1. START push button (NO contact)

X001

2. REVERSE push button for Emergency (NC contact)

X000

3. Limit switch ( a+) for cylinder (A), forward position

(NO contact).

X002

4. Limit switch ( b+) for cylinder (B), forward position.

(NC contact).

X003

Machine actuators

Addresses

1. Solenoid direction valve drives cylinder (A) called VA.

Y022

2. Solenoid directional valve drives cylinder (B) called VB.

Y023

Machine operations

Machine operations cover three stages given as follows:

1. The system is assumed to be in its initial position before the START button has been pressed. We assume both cylinders at their backward or retracted positions. After pressing the START push button, solenoid (A) energized, this will hold the memory of the valve VA; R1, which result in forward movement of cylinder (A).2. Limit switch (a+) which is NO switch, is closed when cylinder A is expanded and results in, breaks or reset the memory of valve VA; R1 i.e solenoid (A) de-energized. Hence cylinder (A) moves backward or retracts. At the same time, solenoid (B) is energized (or setting memory of the valve VB; R2) and result in cylinder (B) movement to the forward direction.

3. Limit switch (b+), which is NC contact, is open when the cylinder (B) reaches the forward position. This result in, solenoid (B) de-energized or breaking the valve memory VB; R2 and cylinder (B) will move to the backward position.

Now the machine cycle is ready for next operation cycle when the operator presses START push-button again. Push button REVERS will reset both memory VA; R1 and VB; R2 in case of Emergency, when pressed by operator which result in both cylinders (A and B) move to backward position. Hence, the machine operation cycle can be written as START, A+, A-, B+, B-.PLC Relay Logic Ladder operation

Stage 1, The initial condition of the system, all the cylinders are at backward positions and all solenoids are de-energized (off state).

Stage 2, When the START push button pressed, the internal relay R1 is energized, which turn the NO contact of R1 in line 2 on the RLL to be closed. This result in energizing the relay solenoid A (having address Y022) and remains energized due to memory R1 in line 2. This will also energize the solenoid valve (A; valve VA) and cylinder (A) will move forward or extend.

Stage 3, when cylinder (A) reaches the extreme position, limit switch ( a+), which has an address of X002, will allow the current flow to internal relay R2, which energizes the solenoid valve (B), having address Y023 (i.e. VB) which results in :

Internal relay R01 will close the contact in line 6 (on RLL) and energizes solenoid valve VB, having address of Y023, this results in forward movement of cylinder (B).

Open the NC contact of the internal relay R1 in line 1 (on RLL), which breaks the memory of the internal relay R1. This results in opening the contact R1 in line 5. This will de-energize the solenoid valve VA, which results in backward movement of the cylinder (A).

Close the contact R2 in line 4, which provide memory to internal relay R2. The cylinder (B) will reach the forward extreme position at which limit switch (b2), (address X003, NC type), is open. This will result in limit switch (b2) open, and the memory of R2 will breaks in line 3, so solenoid (B) de-energized causing cylinder (B) to move backward to its initial position.

7.3 Design Relay Ladder Logic for Sequencing Problems using PLCs.

One of the efficient methods to design sequencing control problems is the CASCADE method [7.1]. This technique can be used to control the sequence of operations of machine sequence having non-sustain control signals or sustain control signals. To illustrate the difference between the two techniques, let us start with the simple technique, which is the machine control sequence, having non-sustain control signals.

7.3.1 Design RLL for Single-Path Machine Sequence Having Non-Sustain Control Signals

This technique based on dividing the machine sequence into groups, such that no opposing output command appears in the same group. In another wards: a new group must be started the moment it becomes necessary to shut off any output actuated during the present group.To describe the technique, consider the given machine sequence having three pneumatic double acting cylinders and having a machine cycle given as follows; START, A+, A-, B+, C+, B-, C-. Note, A+ means forward movement of cylinder A, while A- backward movement for cylinder A. Two limit switches were located at the two extreme positions of the pneumatic cylinder to monitor the cylinder position. Each limit switch is labeled by a small letter having or + sign to indicate its extreme position. For example, a+ letter indicating that the limit switch located at the forward extreme position, while a- letter indicating the backward extreme position, as shown in Fig. 7.3. Each cylinder, e.g. X cylinder, is actuated using a 5/3 directional valve having two solenoids, X+ and X-, respectively, with two return spring to provide the middle position of the directional valve. The middle position of the directional valve will block all the 5 ports of the directional valve, as shown in Fig. 7.3. The left and right positions of the directional valve represent the positions of the cylinder at the two extreme positions, see Fig. 7.3. This type of directional valve will provide a mechanical memory for cylinder movement.

The solenoid X+ must shut off the moment solenoid X- is energized. To achieve this requirement, the given machine sequence can be divided into three groups such that no letter is repeated in any group and given as follows;

Machine control sequence : START, A+, A-, B+, C+, B-, C-.

Group I | Group II | Group III

The relay ladder logic divided into TWO modules called Flip-flop module and Output module.

(1) Flip-flop module :Each group is now allocated by one control relay (internal relay in RLL) used as RS flip-flop (memory). These flip-flops are SET and RESET using the following methods:

Flip-flop SET : 1st group flip-flop is SET using START signal. The 2nd and 3rd groups flip-flops are SET using NO contact of the previous flip-flop connected in series with sensor signal indicating the complement of the last step of the previous group, as shown in Fig.7.4a.

Flip-flop RESET : The reset signal of each flip-flop consists of an NC contact of the next flip-flop. The sensor for the last program step, however, resets the last flip-flop, as shown in Fig. 7.4a.

This way, only ONE flip-flop is SET at any given time or what is called ONE-HOT CODE.

(2) Output module : The output modules of the ladder diagram drawn with various input signals are illustrated directly on the diagram without addressing for the meantime. The address (Y020, Y021, .., X00, X01, ) can be added later.

Note: Two ladder lines connected in parallel (i.e. using two rungs) actuate repeating output signals (such as A+ & A-).

Any output signal that is to appear at the beginning of a new group is produced by an NO contact of the relay assigned to that group. All the other outputs are produced by two contacts in series, which covers: a NO contact of the relay assigned to its group, and the sensor signal indicating the complementation of the previous step. The complete ladder logic diagram is shown in Fig. 7.4(a), while the sequencing chart is given in Fig. 7.5.

7.3.2 Design RLL for Single-Path Machine Sequence Having Sustain Control Signals

The sustained output signal mean that the control signal to be maintained from step to step until the step does not required to be sustained. An example of sustain signal requirement; consider the control sequence of 3 cylinders with 5/2 ways directional valve with spring return. The 3 cylinder operations can be written with sustain signals as follows:

A system of this type requires sustained output signals, the previously described method must be modified. As before, divide the system into groups so that no letter is repeated within any group. Since A-, B-, and C- solenoids do not existing in this problem, and obtained by switching off these solenoids. Hence, the required motions are obtained simply by cut off the respective + solenoid in the output module. As before, the moment a new group is activated, all the outputs of the previous groups are automatically cut off. If it is required to maintain a certain output into the next group, that output has to be maintained in that group. To show this, horizontal lines were drawn on top of the machine sequence for those sustained control signals. For example, B+ must be maintained through part of group II, up to group III just before B-, at this moment, B+ must be cut off, to produce stroke B-,(see Fig. 7.4b). The sequencing chart is also shown in Fig. 7.5.

7.3.3 Design RLL for Multi-Path Sequencing Systems with Sustain Outputs

Cascade method also can be applied to multi-path machine control sequence. Fig. 7.6, schematically shows a program sequence with two (or more than two) simultaneous parallel paths for machine sequence.

The program proceeds as regular sequence up to the completion of step(i). At this point, two parallel paths A and B are carried out simultaneously. Path A has j steps, and path B has k steps; the j and k are not necessarily equal. Only after both paths have been completed AND function, the program continue with the next single-path step(i+1).

The corresponding relay ladder logic is also shown in Fig. (7.6). Only the key ladder lines are indicated, with all output lines omitted for clarity. On completion step i , (xi+ or xi depend on the problem) is actuated, setting flip-flops relay YA1 and YB1. These flip-flops cover one or more steps each, depending on the way paths A and B must be divided into groups. When both parallel paths are completed, sensor signal xAj and xBk are both actuated, that will set the next flip-flop Yi+1 .Note, the normally closed contact yA2 and yB2 (which provide RESET signals for flip-flop YA1 and YB1, respectively) refer to the next flip-flop along the path. For instance, if all of path (A) should belong to same group, then yA2 would become yi+1 . Similarly, contacts yAj and yBk refer to the last flip-flops of the two parallel paths. If all of path (A) should belong to the same group, yAj would be identical with yA1.

Example 7.1 Consider the following machine control sequence with two parallel paths :

The machine sequence can be grouped as follows:

Developed RLL for given machine sequence assuming non-sustain control signals?

The RLL for the given machine sequence is shown in Fig. 7.7

7.3.4 RLL for machine sequence with two or more alternative parallel paths

Some of machine control sequence require two or more alternative parallel sequence. Hence, this required to use multiple RLL sequence for each path. Any parallel machine sequence can be enabled using selector switch/switches, or any other external switch. For example consider Fig. (7.8), after completion of step i, the next step is either A1 or B1 , depending on whether input signal xp has been set to 1 or 0, respectively. This xp signal can be selected manually, e.g. using selector switch, or automatically depending on the outsider machine sequence condition. The machine control sequence will continue along the selected parallel path. Once either path A or B is completed, OR gate function is used, the control sequence will continue with next step i+1.

The keyed RLL for this machine sequence is illustrated in Fig. (7.8), After step i is completed and after switch xI is set logic 1, either flip-flop YA1 or YB1 is set, depending on whether xp = 1 or 0, respectively. Compellation of either step Aj or Bk sets flip-flop Yi+1 .

A RLL with alternative parallel paths is useful for operating multipurpose machines. Programs with more than two alternative parallel paths or more can be applied in the same manner. For example, with n different xp variables (or n switches) required to accommodate 2n alternative paths. Using xp1 and xp2 can be used to accommodate 4 alternative paths : 00, 01, 10 and 11.

Example 7-2 Given the following alternative parallel machine sequence, group the machine sequence using Gascade method and develop the RLL for machine sequence:

The RLL machine sequence as follows, (see Fig.7.9):

7.3.5 RLL for machine sequence with option of bypassing certain steps.

Fig. 7.10, shows a program for machine sequence with the option of bypassing certain machine sequence steps. At the completion of step i, if input control signal xp =1, then the system goes through program steps from A1 to Aj , and continue with step I+1. If, on the other hand, xp = 0, then the system jumps directly from step I to I+1.

The keyed RLL for machine sequence is shown in Fig. 7.10. It can be observed that flip-flop Yi can be reset by either yA1 or yi+1 . Flip-flop YA1 is set by the ANDing function xp xI yI and rest by yA2 (or by yI+1 if the by passed section is all included in one group). Flip-flop YI+1 is set by either the AND function xp xI yI or xAJ yAJ .

Example 7.3 Develop the RLL for machine sequence with option bypassing certain steps:

START, A+ , , A- .

G1

G4

The RLL for the given machine sequence is shown in Fig. (7.11).

7.3.6 RLL for machine sequence with the option of repeating certain steps.

Fig. 7.12, shows a multi-path machine sequence with the option of repeating certain steps. At the completion of step Aj , the system will continue with step i+1, provided xp =1 . If, however, xp = 0 , then steps A1 to AJ are repeated indefinitely until xp becomes 1. This circuit is suitable for machine sequence to be repeated until the desired effect is achieved.

The corresponding keyed RLL for this machine sequence is illustrated in Fig. (7.12). It can be seen that the flip-flop YA1 can be set using AND function either xi yi OR by xp xAj yAj and reset using yA2 . Furthermore, the flip-flop yAj is reset by either yA1 OR yI+1 , depending on weather the machine steps are repeated or not.

Note; at least three flip-flops must be allocated for repeated machine steps. If only one or two flip-flops were assigned for the repeated machine steps, they will set and reset simultaneously and multifunction would occur. Even the rule to divide the machine sequence into groups calls for only two groups to cover the repeated steps, a third dummy group must be added. Completion of the last repeated step sets this dummy flip-flop, and the sequence carries on from there, depending whether xp=0 or 1.

Example 7.4 Develop the RLL for a machine sequence with option repeated certain machine steps:

The RLL for the given machine sequence shown in Fig. 7.13 (note, group G4 is added as dummy group to include three groups, as minimum, for repeated machine sequence steps).

PROPLEMS:

7.1) Develop the sequencing chart for the following machine cycles using double acting cylinder having two limit switches, at the two extreme positions. Solve the problem assuming non-sustain control signals (5/3 double solenoids and two spring for valve center);

a) START, A+, A-, A+, A-, B+, B-.

b) START, A+, B+, B-, B+, B-, A-.

c) START, A+, A-, B+, C+, B-, C-.

d) START, A+, B+, A-, A+, B-, A-.

e) START, A+, B+, A-, B-, A+, A-.

7.2) Group the machine cycles given in Prob. 7.1 using Cascade method then develop the RLL?7.3) Resolve Problem 7.1 using sustain control signals (5/2 solenoid valve with return spring)?

7.4) Resolve Problem 7.2 using sustain control signals (5/2 solenoid valve with return spring)?

7.5) Group the following parallel path machine cycles using Cascade method, develop the sequencing chart, and RLL using non-sustain control signals;

a)

b)

7.6) Group the following machine cycles using Cascade method and develop the RLL for the given machine sequence having three alternative paths and using two selector switches Xp1 and Xp2. The machine sequence given as follows (assume non-sustain control signal for cylinders B,C and D, while sustain control signal for cylinder A ):

7.7) Group the following machine cycle using Cascade method and develop the RLL for the given machine sequence having two alternative paths and bypass machine cycle path. The selection of machine paths and bypass path is achieved using two selector switches Xp1 and Xp2. The machine sequence given as follows(assuming non-sustain control signals for all cylinders):

7.8) Develop RLL for machine sequence with optional repeat machine steps. The selection of repeated machine path is achieved using two selector switches xp1 and xp2 for the machine sequence given as follows (assuming non-sustain control signal for all cylinders):

7.9) Resolve Prob. 7.8 by adding alternative path of machine sequence as illustrated below:

REFERENCES:[7.1] : David W. Pessen, Industrial Automation, Circuit Design & Components

, A Wiley-Interscience Publication, John Wiley & Sons, 1989.

Switch address

StartX0

E.StopX1

.a+ X2

.a- X3

.b+ X6

.b- X7

Xp XA

Output Address

A+Y22

A - Y23

B+Y24

B -Y25

START R2 R4 E.Stop R1

R1

R1 Xp a+ R3 E.Stop R2

R2

R2 Xp b+ R4 E.Stop R3

R3

R1 Xp a+ a- E.Stop R4

R3 b-

R4

R1 A+

R4 A-

R2 B+

R3 B-

Fig. 7.11 The developed RLL for machine sequence with option bypassing machine steps (for example 7.3).

i-1 i A1 A2 Aj-1 Aj i+1 xp=1

xp=0

Xp=1; ( B+, B-)

G2 | G3

Xp=0; by pass

Fig. 7.10 Keyed RLL for machine sequence with option bypassing certain steps.

i-1 i xp=1 A1 A2 Aj-1 Aj i+1 ..

xp=0

.yi-1 yA1 yi+1 Yi

yi

yi xp xi yA2 or yi+1 YA1

yA1

yi xp xi yi+2 Yi+1

yAi xAj

yi+1

Path2

Path1

Switch address

StartX0

E.StopX1

.a+ X2

.a- X3

.b+ X6

.b- X7

.c+ X8

.c- X9

.Xp XA

Output Address

A+Y22

A - Y23

B+Y24

B -Y25

C+Y26

C -Y27

Output Module

Start R02 R04 E.Stop R01

R01

R01 Xp a+ R03 E.Stop R02

R02

R02 Xp b+ R06 E.Stop R03

R03

R01 Xp a+ R05 E.Stop R04

R04

R04 Xp c+ R06 E.Stop R05

R05

R03 c+ c- E.Stop R06

R05 b-

R06

R1 A+

R6A-

R2B+

R4

R3B-

R5

R3 b- C+

R4 b+

R6 a- C-

Fig. 7.9 RLL for alternative machine sequence (for example 7.2).

Laboratory Work 7.2 : Simulate the machine sequences for examples 7.1 to 7.4 using Toshiba PLC.

Exercise: Modify the above example to carry out the following control sequence ;

START push button.

Cylinder (A) forward and keep it in the forward position.

Cylinder (B) forward.

All cylinders (A) & (B) backward.

Machine cycle will be ; START, A+, B+,A-,B-.

Laboratory work 7.1 : Simulates the machine cycle given in the illustrated above example and exercise, using TOSHIBA PLCs.

EMBED Equation.3

Fig. 7.8 Machine sequence, keyed RLL with two alternative parallel paths.

yi-1 yA1 yB1 Yi

yi

yi xp xi yA2 or yi+1 YA1

yA1

yi xp xi yB2 or yi+1 YB1

yB1

yAJ xAJ yi+2 Yi+1

yBK xBK

yi+1

i-1 i xp=1 A A2 Aj-1 Aj i+1 ..

xp=0

B1 B2 Bk-1 Bk

EMBED Equation.3

EMBED Equation.3

Fig. 7.7 RLL of two parallel paths with non-sustain control signals (for example 7.1)

Input switchesAddress

StartX00

a+ X01

a-X02

b+X04

b-X05

c+X06

.c- X07

STOP X03

Group memoryAddress

Flip-flop1R01

Flip-flop2R02

Flip-flop3R03

Flip-flop4R04

Flip-flop5R05

OutputsAddress

A+Y25

A-Y26

B+Y27

B-Y28

C+Y29

C-Y2A

START R02 STOP R01

R01

R01 a+ R03 STOP R02

R02 R04 Flip-flop

Modules.

R02 a- R05 STOP R03

R03

R02 a- R05 STOP R04

R04

R03 R04 b+ c+ c- STOP R05

R05

R01 A+

R03

R02 A- Output Modules

R05

R03 a+ B+

R05 a- B-

R04 C+

R05 b- C-

.yAj yBk XAj XBk yi+2 Yi+1

.yi+1

.yi Xi yB2 ( or yi+1 ) YB1

.yB1

.yi Xi yA2 ( or yi+1 ) YA1

.yA1

.yi-1 yA1 Yi

.yi yB1

A1 A2 Aj

i .i+1

B1 B2 Bk

Fig. 7.5 Sequencing chart for machine cycle START,A+,A-,B+,C+,B-,C-.

A+

A-

B+

Cylds. B-

C+

C-

A+

A-

B+

Solds. B-

Non-sus C+

C-

Solds A

sus B

C

. a+

a-

b+

Switches b-

c+

c-

START

| Group I | Group II | Group III |

I II III IV V VI VII VIII IX X

START A+ A- B+ C+ B- C-

Machine control sequence : START, A+, A-, B+, C+, B-, C-.

Group I | Group II | Group III

R01 A+

R02 a- B+

R02 b+ C+

R03 b- Output

Modules

(b) Relay ladder logic with sustain outputs

Input switchesAddress

Start X00

a+ X01

a- X02

b+ X04

b- X05

c+ X06

.c- X07

STOP(not shown) X03

Group memoryAddress

Flip-flop1 R01

Flip-flop2 R02

Flip-flop3 R03

OutputsAddress

A+ Y20

A- Y21

B+ Y22

B- Y23

C+ Y24

C- Y25

START R02 R01

R01

R01 a+ R03 R02

R02 Flip-flop

Modules.

R02 c+ c- R03

R03

R01 A+

R02 A-

R02 a- B+

R03 B- Output

Modules

R02 b+ C+

R03 b- C-

(a) Relay ladder logic without sustain outputs

Fig. 7.4 Relay ladder logic for machine sequence START, A+, A-, B+, C+, B-, C-. (a) without sustain outputs, (b) with sustain outputs.

- X +

Sol X- Sol X+

Fig. 7.3, Cylinder X operation having two electric limit switches x+ and x- showing two- solenoid valve 5/3 symbol with two-spring return.

- X +

x+

x-

L 1

L 2

L3

L4

L5

L6

Cylinders

Limit switches

Memory relay

Solenoids

A+

A-

B+

B-

.a+

..b+

START

R1

R2

A+

B+

I II III IV V VI

R2

R1

R2

.a+ b+

R1

REVERS START a+

B+

Fig 7.6 Simultaneous parallel machine sequence and keyed RLL.

A+

B+

A+

.b+

- B +

R2

.a+

R1

- A +

Fig. 7.2 Relay ladder logic (RLL) developed using sequencing chart to control two double acting cylinders using 5/2 solenoid valve with return spring and two limit switches. Machine sequence START, A+,A-,B+,B-

A1 A2 A3 A.. An-1 An An+1 (a)

Ak Ak+1 A Aj-1 Aj Aj+1 (b)

Bk+1 B Bj-1

Ck+1 C Cj-1

I xp=1 A1 A.. Aj I+1 I+2 (c)

.xp=0 B1 B.. Bk

I xp=0 A1 A.. Aj I+1 I+2 (d)

I A1 A2 A.. Aj xp=0 Aj+1 (e)

Fig. 7.1 Common machine sequence used by industry.

Single path machine sequence.

Parallel path machine sequence.

Parallel path machine sequence with two or more alternative path selection.

Single path machine sequence with option bypass machine sequence.

Single path machine sequence with optional repeat certain steps.

.xp=1

.xp=1

Fig. 7.12 Keyed RLL for machine sequence with option of repeat machine sequence steps.

yi-1 yA1 Yi

yi

yi xi yA2 YA1

yAj xp xAj

yA1

yA1 xA1 yA3 or yAj YA2

yA2

yAj-1 xAj-1 yi+1 yA1 YAj

yAj

yAj xp xAj yi+2 Yi+1

yi+1

Fig. 7.13 RLL for machine sequence with option of repeat machine sequence steps (example 7.4).

START R2 E.STOP R1

R1

R1 a+ R3 E.STOP R2

R4 xp c-

R2

R2 c+ R4 E.STOP R3

R3

R3 b- R5 R2 E.STOP R4

R4

R4 xp c- a- E.STOP R5

R5

R1A+

R5A-

R2B+

R3B-

R2 b+ C+

R4C-

Input address

StartX0

E.StopX1

.a+ X2

.a-X3

.b+X6

.b-X7

.c+X8

.c-X9

.xpXA

Output address

A+Y21

A -Y22

B+Y23

B -Y24

C+Y25

C -Y26

PAGE 7.8

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