Siemens S7-200 user guide: Sample Programs for the Position Module

Sample Programs for the Position Module

The first sample program shows a simple relative move that uses the POSx_CTRL and POSx_GOTO instructions to perform a cut-to-length operation. This program does not require an RP seek mode or a motion profile, and the length can be measured in either pulses or engineering units. Enter the length (VD500) and target speed (VD504). When I0.0 (Start) turns on, the machine starts. When I0.1 (Stop) turns on, the machine finishes the current operation and stops. When I0.2 (E_Stop) turns on, the machine aborts any motion and immediately stops.

The second sample program provides an example of the POSx_CTRL, POSx_RUN, POSx_RSEEK, and POSx_MAN instructions. You must configure the RP seek mode and a motion profile.

Sample Program 1: Simple Relative Move (Cut to Length application)

Sample Program 1: Simple Relative Move (Cut to Length application) , continued

\begin{tabular}{p{0.45\textwidth} p{0.45\textwidth}} \textbf{Network 6} & \textbf{Network 6} //When the cut is finished then restart \ & //unless the Stop is active. \ Running:Q0.2 \quad T33 \quad Stop:I0.1 \quad Start_Next_Move:M0.1 & LD \quad Q0.2 \ & A \quad T33 \ & LPS \ & AN \quad I0.1 \ & = \quad M0.1 \ & LPP \ & A \quad I0.1 \ & R \quad Q0.2, 1 \ \end{tabular}

Sample Program 2: Program with POSx_CTRL, POSx_RUN, POSx_SEEK, and POSx_MAN

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Sample Program 2: Program with POSx_CTRL, POSx_RUN, POSx_SEEK, and POSx_MAN, continued

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Sample Program 2: Program with POSx_CTRL, POSx_RUN, POSx_SEEK, and POSx_MAN, continued

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Sample Program 2: Program with POSx_CTRL, POSx_RUN, POSx_SEEK, and POSx_MAN, continued

Network 16 //Unless STOP is on, restart //when the cut is finished. LD T33 LPS R Q0.3, 1 R Q0.4, 1 AN I0.2 SCRT S0.1 LPP A I0.2 R M0.0, 4

Network 17 SCRE

Network 18 LSCR S1.0

Network 19 //Reset the outputs. LD S1.0 R Q0.3, 2

Network 20 //Flash the error light. LD SM0.5 = Q0.5

Network 21 //Exit the error routine if STOP is on. LD I0.2 R M0.0, 9 R S0.1, 8

Network 22 SCRE

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Monitoring the Position Module with the EM 253 Control Panel

To aid you in the development of your Position Control solution, STEP 7-Micro/WIN provides the EM 253 Control Panel. The Operation, Configuration and Diagnostics tabs make it easy for you to monitor and control the operation of the Position module during the startup and test phases of your development process.

Use the EM 253 Control Panel to verify that the Position module is wired correctly, to adjust the configuration data, and to test each movement profile.

Displaying and Controlling the Operation of the Position Module

The Operation tab of the control panel allows you to interact with the operations of the Position Module. The control panel displays the current speed, the current position and the current direction of the Position module. You can also see the status of the input and output LEDs (excluding the Pulse LEDs).

The control panel allows you to interact with the Position module by changing the speed and direction, by stopping and starting the motion, and by jogging the tool (if the motion is stopped).

You can also generate the following motion commands:

Enable Manual Operation. This command allows you to use the manual controls for positioning the tool.

Run a Motion Profile. This command allows you to select a profile to be executed. The control panel displays the status of the profile which is being executed by the Position module.

Figure 9-17 Operation Tab of the EM 253 Control Panel

Seek to a Reference Point. This command finds the reference point by using the configured search mode.

Load Reference Point Offset. After you use the manual controls to jog the tool to the new zero position, you then load the Reference Point Offset.

Reload Current Position. This command updates the current position value and establishes a new zero position.

Activate the DIS output and Deactivate the DIS output. These commands turn the DIS output of the Position module on and off.

Pulse the CLR output. This command generates a 50 ms pulse on the CLR output of the Position module.

Teach a Motion Profile. This command allows you to save the target position and speed for a motion profile and step as you manually position the tool. The control panel displays the status of the profile which is being executed by the Position module.

Load Module Configuration. This command loads a new configuration by commanding the Position module to read the configuration block from the V memory of the S7-200.

Open Loop Motion Control with the S7-200 Chapter 9

Move to an Absolute Position. This command allows you to move to a specified position at a target speed. Before using this command, you must have already established the zero position.

Move by a Relative Amount. This command allows you to move a specified distance from the current position at a target speed. You can enter a positive or negative distance.

Reset the Command Interface. This command clears the command byte for the Position module and sets the Done bit. Use this command if the Position module appears to not be responding to commands.

Displaying and Modifying the Configuration of the Position Module

The Configuration tab of the control panel allows you to view and modify the configuration settings for the Position module that are stored in the data block of the S7-200.

After you modify the configuration settings, you simple click a button to update the settings in both the STEP 7-Micro/Win project and the data block of the S7-200.

Figure 9-18 Configuration Tab of the EM 253 Control Panel

Displaying the Diagnostics Information for the Position Module

The Diagnostics tab of the control panel allows you to view the diagnostic information about the Position module.

You can view specific information about the Position module, such as the position of the module in the I/O chain, the module type and firmware version number, and the output byte used as the command byte for the module.

The control panel displays any error condition that resulted from a commanded operation. Refer to Table 9-20 for the instruction error conditions.

You can also view any error condition reported by the Position module. Refer to Table 9-21 for the module error conditions.

Figure 9-19 Diagnostics Tab of the EM 253 Control Panel

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Error Codes for the Position Module and the Position Instructions

Table 9-20 Instruction Error Codes

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Table 9-21 Module Error Codes

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Advanced Topics

Understanding the Configuration/Profile Table

The Position Control wizard has been developed to make motion applications easy by automatically generating the configuration and profile information based upon the answers you give about your position control system. Configuration/profile table information is provided for advanced users who want to create their own position control routines.

The configuration/profile table is located in the V memory area of the S7-200. As shown in Table 9-22, the configuration settings are stored in the following types of information:

☐ The configuration block contains information used to set up the module in preparation for executing motion commands.

☐ The interactive block supports direct setup of motion parameters by the user program.

☐ Each profile block describes a predefined move operation to be performed by the Position module. You can configure up 25 profile blocks.

Tip To create more than 25 motion profiles, you can exchange configuration/profile tables by changing the value stored in the configuration/profile table pointer.

Table 9-22 Configuration/Profile Table

Table 9-22 Configuration/Profile Table, continued

Table 9-22 Configuration/Profile Table, continued

Open Loop Motion Control with the S7-200 Chapter 9

Table 9-22 Configuration/Profile Table, continued

Special Memory Locations for the Position Module

The S7-200 allocates 50 bytes of special memory (SM) to each intelligent module, based on the physical position of the module in the I/O system. See Table 9-23. When the module detects an error condition or a change in status of the data, the module updates these SM locations. The first module updates SMB200 through SMB249 as required to report the error condition, the second module updates SMB250 through SMB299, and so on.

Table 9-23 Special Memory Bytes SMB200 to SMB549

Table 9-24 shows the structure of the SM data area allocated for an intelligent module. The definition is given as if this were the intelligent module is located in slot 0 of the I/O system.

Table 9-24 Special Memory Area Definition for the EM 253 Position Module

Understanding the Command Byte for the Position Module

The Position module provides one byte of discrete outputs which is used as the command byte. Figure 9-20 shows the command byte definition. Table 9-20 shows the Command_code definitions.

A write to the command byte where the R bit changes from 0 to 1 is interpreted by the module as a new command.

If the module detects a transition to idle (R bit changes state to 0) while a command is active, then the operation in progress is aborted and, if a motion is in progress, then a decelerated stop is performed.

After an operation has completed, the module must see a transition to idle before a new command is accepted. If an operation is aborted, then the module must complete any deceleration before a new command is accepted. Any change in the Command_code value while a command is active is ignored.

The response of the Position module to a change in the operating mode of the S7-200 or to a fault condition is governed by the effect that the S7-200 exerts over the discrete outputs according to the existing definition of the S7-200 function:

• If the S7-200 changes from STOP to RUN: The program in the S7-200 controls the operation of the Position module.
• If the S7-200 changes from RUN to STOP: You can select the state that the discrete outputs are to go to on a transition to STOP or that the outputs are to retain their last state.
  • If the R bit is turned off when going to STOP: The Position module decelerates any motion in progress to a stop
  • If the R bit is turned on when going to STOP: The Position module completes any command that is in progress. If no command is in progress, the Position module executes the command which is specified by the Command_code bits.
  • If the R bit is held in its last state: The Position module completes any motion in progress.
• If the S7-200 detects a fatal error and turns off all discrete outputs: The Position module decelerates any motion in progress to a stop.

The Position module implements a watchdog timer that turns the outputs off if communications with the S7-200 are lost. If the output watchdog timer expires, the Position module decelerates any motion in progress to a stop.

If a fatal error in the hardware or firmware of the module is detected, the Position module sets the P0, P1, DIS and CLR outputs to the inactive state.

Figure 9-20 Definition of the Command Byte

Table 9-25 Command_code Definitions

Table 9-26 Motion Commands

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Table 9-26 Motion Commands, continued

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Understanding the Profile Cache of the Position Module

The Position module stores the execution data for up to 4 profiles in cache memory. When the Position module receives a command to execute a profile, it checks to see if the requested profile is stored in the cache memory. If the execution data for the profile is resident in the cache, the Position module immediately executes the profile. If the the execution data for the profile is not resident in the cache, the Position module reads the profile block information from the configuration/profile table in the S7-200 and calculates the execution data for the profile before executing the profile.

Command 122 (Execute the motion specified in the interactive block ) does not use cache memory to store the execution data, but always reads the interactive block from the configuration/profile table in the S7-200 and calculates the execution data for the motion.

Reconfiguring the Position module deletes all of the execution data stored in the cache memory.

Creating Your Own Position Control Instructions

The Position Control wizard creates the position instructions for controlling the operation of the Position module; however, you can also create your own instructions. The following STL code segment provides an example of how you might create your own control instructions for the Position module.

This example uses an S7-200 CPU 224 with a Position module located in slot 0. The Position module is configured on power-up. CMD_STAT is a symbol for SMB234, CMD is a symbol for QB2, and NEW_CMD is a symbol for the profile.

Sample Program: Controlling the Position Module Network 1 //New move command state LSCR State_0

Network 2 //CMD_STAT is a symbol for SMB234 //CMD is a symbol for QB2 //NEW_CMD is a symbol for the profile. // //1. Clear the Done bit of the Position module. //2. Clear the command byte of the Position module. //3. Issue the new command. //4. Wait for the command to be executed. LD SM0.0 MOVB 0, CMD_STAT BIW 0, CMD BIW NEW_CMD, CMD SCRT State_1

Network 3 SCRE

Network 4 //Wait for the command to be completed. LSCR State_1

Network 5 //If the command is complete without error, go to the idle state. LDB= CMD_STAT, 16#80 SCRT Idle_State

Network 6 //If the command is complete with an error, go to the error handling state. LDB> CMD_STAT, 16#80 SCRT Error_State

Network 7 SCRE

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Understanding the RP Seek Modes Supported by the Position Module

The following figures provide diagrams of the different options for each RP seek mode.

☐ Figure 9-21 shows two of the options for RP seek mode 1. This mode locates the RP where the RPS input goes active on the approach from the work zone side.

☐ Figure 9-22 shows two of the options for RP seek mode 2. This mode locates the RP in the center within the active region of the RPS input.

☐ Figure 9-23 shows two of the options for RP seek mode 3. This mode locates the RP a specified number of zero pulses (ZP) outside the active region of the RPS input.

☐ Figure 9-24 shows two of the options for RP seek mode 4. This mode locates the RP a specified number of zero pulses (ZP) within the active region of the RPS input.

For each mode, there are four combinations of RP Seek direction and RP Approach direction. (Only two of the combinations are shown.) These combinations determine the pattern for the RP seek operation. For each of the combinations, there are also four different starting points:

The work zones for each diagram have been located so that moving from the reference point to the work zone requires movement in the same direction as the RP Approach Direction. By selecting the location of the work zone in this way, all the backlash of the mechanical gearing system is removed for the first move to the work zone after a reference point seek.

Figure 9-21 RP Seek Mode 1

Default configuration : RP Seek Direction: Negative RP Approach Direction: Positive

LMT- Active

RPS Active RP

Work Zone

Positive motion Negative motion

RP Seek Direction: Positive RP Approach Direction: Positive

RPS Active RP

Work Zone

LMT+ Active

Positive motion Negative motion

Figure 9-22 RP Seek: Mode 2

Default configuration : RP Seek Direction: Negative RP Approach Direction: Positive

LMT- Active

RPS Active RP

Work Zone Number of ZP pulses

Positive motion Negative motion

RP Seek Direction: Positive RP Approach Direction: Positive

RPS Active RP

Work Zone Number of ZP pulses

LMT+ Active

Positive motion Negative motion

Figure 9-23 RP Seek: Mode 3

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Default configuration : RP Seek Direction: Negative RP Approach Direction: Positive

LMT - Active RPS Active RP Work Zone Number of ZP pulses Positive motion Negative motion

RP Seek Direction: Positive RP Approach Direction: Positive

RPS Active RP Work Zone Number of ZP pulses LMT+ Active Positive motion Negative motion

Figure 9-24 RP Seek: Mode 4

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Selecting the Location of the Work Zone to Eliminate Backlash

Figure 9-25 shows the work zone in relationship to the reference point (RP), the RPS Active zone, and the limit switches (LMT+ and LMT-) for an approach direction that eliminates the backlash. The second part of the illustration places the work zone so that the backlash is not eliminated. Figure 9-25 shows RP seek mode 3. A similar placement of the work zone is possible, although not recommended, for each of the search sequences for each of the other RP seek modes.

Figure 9-25 Placement of the Work Zone with and without the Elimination of Backlash

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Creating a Program for the Modem Module

The EM 241 Modem module allows you to connect your S7-200 directly to an analog telephone line, and supports communications between your S7-200 and STEP 7-Micro/WIN. The Modem module also supports the Modbus slave RTU protocol. Communications between the Modem module and the S7-200 are made over the Expansion I/O bus.

STEP 7-Micro/WIN provides a Modem Expansion wizard to help set up a remote modem or a Modem module for connecting a local S7-200 to a remote device.

I n This Chapter

• Features of the Modem Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........ 308
• Using the Modem Expansion Wizard to Configure the Modem Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........ 314
• Overview of Modem Instructions and Restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........

Features of the Modem Module

The Modem module allows you to connect your S7-200 directly to an analog telephone line and provides the following features:

Provides international telephone line interface

Provides a modem interface to STEP 7-Micro/WIN for programming and troubleshooting (teleservice)

Supports the Modbus RTU protocol

Supports numeric and text paging

Supports SMS messaging

Allows CPU-to-CPU or CPU-to Modbus data transfers

Provides password protection

Provides security callback

The Modem module configuration is stored in the CPU

Figure 10-1 EM 241 Modem Module

You can use the STEP 7-Micro/WIN Modem Expansion wizard to configure the Modem module. Refer to Appendix A for the specifications of the Modem module.

International Telephone Line Interface

The Modem module is a standard V.34 (33.6 kBaud), 10-bit modem, and is compatible with most internal and external PC modems. The Modem module does not communicate with 11-bit modems.

You connect the Modem module to the telephone line with the six-position four-wire RJ 11 connector mounted on the front of the module. See Figure 10-2.

An adapter may be required to convert the RJ 11 connector for connection to the standard telephone line termination in the various countries. Refer to the documentation for your adapter connector for more information.

The modem and telephone line interface is powered from an external 24 VDC supply. This can be connected to the CPU sensor supply or to an external source. Connect the ground terminal on the Modem module to the system earth ground.

The Modem module automatically configures the telephone interface for country-specific operation when power is applied to the module. The two rotary switches on the front of the module select the country code. You must set the switches to the desired country selection before the Modem module is powered up. Refer to Table 10-1 for switch settings for the countries supported.

Figure 10-2 View of RJ 11 Jack

Table 10-1 Countries Supported by the EM 241

\begin{tabular}{ll} \hline Switch Setting & Country \ \hline 00 & Australia \ 01 & Austria \ 02 & Belgium \ 05 & Canada \ 06 & China \ 08 & Denmark \ 09 & Finland \ 10 & France \ 11 & Germany \ 12 & Greece \ 16 & Ireland \ 18 & Italy \ 22 & Luxembourg \ 25 & Netherlands \ 26 & New Zealand \ 27 & Norway \ 30 & Portugal \ 34 & Spain \ 35 & Sweden \ 36 & Switzerland \ 38 & U.K. \ 39 & U.S.A. \ \hline \end{tabular}

Creating a Program for the Modem Module Chapter 10

STEP 7-Micro/WIN Interface

The Modem module allows you to communicate with STEP 7-Micro/WIN over a telephone line (teleservice). You do not need to configure or program the S7-200 CPU to use the Modem module as the remote modem when used with STEP 7-Micro/WIN.

Follow these steps to use the Modem module with STEP 7-Micro/WIN:

1. Remove the power from the S7-200 CPU and attach the Modem module to the I/O expansion bus. Do not attach any I/O modules while the S7-200 CPU is powered up.
2. Connect the telephone line to the Modem module. Use an adapter if necessary.
3. Connect 24 volts DC to the Modem module terminal blocks.
4. Connect the Modem module terminal block ground connection to the system ground.
5. Set the country code switches.
6. Power up the S7-200 CPU and the Modem module.
7. Configure STEP 7-Micro/WIN to communicate to a 10-bit modem.

Modbus RTU Protocol

You can configure the Modem module to respond as a Modbus RTU slave. The Modem module receives Modbus requests over the modem interface, interprets those requests and transfers data to or from the CPU. The Modem module then generates a Modbus response and transmits it out over the modem interface.

Tip
If the Modem module is configured to respond as a Modbus RTU slave, STEP 7-Micro/WIN is not able to communicate to the Modem module over the telephone line.

The Modem module supports the Modbus functions shown in Table 10-2.

Modbus functions 4 and 16 allow reading or writing a maximum of 125 holding registers (250 bytes of V memory) in one request. Functions 5 and 15 write to the output image register of the CPU. These values can be overwritten by user program.

Modbus addresses are normally written as 5 or 6 character values containing the data type and the offset. The first one or two characters determine the data type, and the last four characters select the proper value within the data type. The Modbus master device maps the addresses to the correct Modbus functions.

Table 10-2 Modbus Functions Supported by Modem Module

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