1. Overview: SIMATIC TM PTO 4 for S7-1500 Pulse Train Output
The SIMATIC TM PTO 4 (article number 6ES7553-1AA01-0AB0) is a technology module that adds four independent pulse train output (PTO) channels to a SIMATIC S7-1500 CPU or to an ET 200MP distributed I/O station. Each channel generates a pulse/direction (PTO) signal pair that drives a third-party stepper or servo drive that accepts a PTI (Pulse Train Input) interface. The module is the dedicated S7-1500 replacement for the embedded PTO outputs that exist on selected S7-1200 CPUs, and it is the only Siemens catalog product that exposes pulse-train motion control on the S7-1500/ET 200MP platform.
The TM PTO 4 closes a long-standing gap for engineers migrating motion control projects from the S7-1200 to the S7-1500. On the S7-1500, the CPU itself does not expose PTO outputs; instead, the TM PTO 4 plugs into the S7-1500/ET 200MP backplane and routes pulse streams to external drives. Because the module counts every pulse it transmits, it can return an actual position value to the PLC even when the connected motor has no shaft encoder – the typical configuration for low-cost stepper drives. This is explicitly stated in the device manual: "The number of steps that are output is returned as the actual position value."
The module went on sale in early 2017, and a reworked V2.0 hardware/firmware variant was released later. The original print manual (A5E38896703-AA, edition 12/2016) is now superseded by the online entry in the TIA Portal manual collection.
2. Module Identification, Catalog Numbers, and Variants
| Feature | Value |
|---|---|
| Article number (MLFB) | 6ES7553-1AA01-0AB0 |
| Designation | SIMATIC TM PTO 4 – Technology Module, 4-channel pulse train output |
| Target system | SIMATIC S7-1500 / ET 200MP |
| Number of PTO channels | 4 (independent) |
| Drive interface | PTO – pulse and direction, drives with PTI (Pulse Train Input) |
| Position feedback to PLC | Internal pulse counter (no encoder required on motor) |
| Original release | February 2017 (V1.0) |
| V2.0 release (reworked) | See Sales release: Version 2 of the S7-1500 TM PTO 4 |
| Original manual reference | A5E38896703-AA, edition 12/2016 |
| Current documentation hub | TM PTO 4 Technology Module (6ES7553-1AA01-0AB0) |
-0AB0 suffix is the standard Siemens MLFB termination for the original release. When ordering spare or replacement units, confirm the firmware on the existing module matches the TIA Portal HSP/GSD you are using; V1.x and V2.x firmware can co-exist on the same TIA Portal version but require the matching device version in the device configuration.3. Hardware Installation and Slot Rules
The TM PTO 4 is a 35 mm-wide S7-1500/ET 200MP module that mounts on the standard DIN rail and is connected to the backplane bus like any other S7-1500 I/O module. Observe the S7-1500 system rules before selecting a slot:
- Slot location. The TM PTO 4 must be installed in a slot to the right of the CPU (or right of the S7-1500 interface module on ET 200MP) in the same way as other technology modules such as TM Timer DIDQ, TM Count, or TM PosInput.
- Maximum technology modules per station. The number of allowed technology modules per S7-1500 CPU depends on the CPU firmware and project memory. Check the CPU manual for the active limit; many S7-1500 CPUs permit a generous number, but every technology object (TO) consumes work memory.
- Power supply. Each channel provides 24 V DC output signals. The module does not require a separate load voltage group beyond what the backplane supplies; verify the wiring diagram in the device manual for the exact terminal assignments.
- Shielding and grounding. Use shielded twisted-pair cable from each channel to the drive's PTI input. Ground the shield at the cabinet entry with a low-impedance connection; the TM PTO 4 front connector exposes shield terminals.
- Mechanical coding. Code the front connector mechanically to the module to prevent miswiring during field replacement.
4. Channel Architecture and PTO Signal Topology
Each of the four channels is electrically and logically independent. A channel exposes a pulse output and a direction output (and, depending on firmware, additional control lines such as enable and ready). The drive decodes the pulse stream: one rising edge (or one pulse, depending on drive configuration) equals one motor step or one encoder increment in position mode.
The PLCopen MC_MoveAbsolute / MC_MoveRelative / MC_MoveVelocity blocks feed the technology object, which in turn commands the TM PTO 4 hardware to emit the correct number of pulses at the programmed velocity and acceleration. The number of pulses the module actually emits is counted internally and returned as the axis ActualPosition. This makes open-loop stepper control practical on S7-1500 without requiring an external encoder.
5. Pulse/Direction Timing Reference
The drive's PTI input determines how it interprets each pulse. The most common interpretations are "count a step on each rising edge" and "count one step per quadrature cycle." The TM PTO 4 firmware is configured in TIA Portal to match what the drive expects. The general timing model is:
The drive is responsible for executing the microstep lookup, current loop, and stall handling. The PLC only sees the high-level ActualPosition in user units (e.g., mm or degrees), not raw pulse counts.
6. TIA Portal Configuration Procedure
6.1 Prerequisites
- TIA Portal V16 or newer (consult the TM PTO 4 readme for the exact TIA Portal versions that support V1.x vs V2.x firmware).
- S7-1500 CPU with a free slot to the right of the CPU (or after the IM in an ET 200MP station).
- Installed HSP/GSD for the TM PTO 4 module, matching the firmware you intend to use.
- Drive datasheet confirming the PTI input voltage and pulse-edge convention (rising-edge or quadrature).
6.2 Step-by-Step Setup
- Add the TM PTO 4 to the device configuration. In the project tree, open Devices & Networks, drag the S7-1500 CPU onto the project, then open Device view. In the hardware catalog navigate to Technology modules → TM PTO 4 (6ES7553-1AA01-0AB0) and drag the module into the first free slot to the right of the CPU.
- Select the device version. Right-click the module → Properties → General → Device version. Choose V1.x or V2.x to match the physical module's firmware label.
- Configure the PTO outputs. In the module's properties enable the channels you intend to use (up to four). For each enabled channel, assign the front connector terminals you will wire.
- Create the technology object. In the project tree, expand the CPU → Technology objects → Add new object. Choose PositioningAxis. In the wizard, set Drive connection to TM PTO and select the matching PTO channel. The TO is now bound to that channel.
- Configure mechanics. In the TO configuration set the increments per motor revolution, the load revolutions per motor revolution (gear ratio), the load increments per load revolution, and the user unit (mm, °, increments). TIA Portal converts all motion commands into pulse counts automatically.
- Configure dynamics. Set maximum velocity, acceleration, deceleration, and jerk. The drive's maximum pulse rate limits the achievable velocity; consult the TM PTO 4 manual for the maximum pulse frequency.
- Configure homing. Choose active or passive homing that matches your machine. With an open-loop stepper and no hardware home switch, you can use the drive's Z-pulse or a software-only homing sequence – but be aware that absolute position is lost after power-off without an absolute encoder or battery-backed multi-turn counter.
- Compile and download. Compile the hardware and software, then download to the CPU. After download, TIA Portal offers Commissioning → Axis control panel for one-axis jogging and diagnostic visualization.
ActualPosition counter and the drive's actual position – they must increment in the same direction and by the same amount per commanded jog step.7. Programming with PLCopen Motion Blocks
The TO PositioningAxis presents the standard Siemens PLCopen interface: MC_Power, MC_Reset, MC_MoveAbsolute, MC_MoveRelative, MC_MoveVelocity, MC_Stop, MC_Home, and the read-only MC_ReadActualPosition / MC_ReadActualVelocity. A typical ladder snippet to drive the axis from a start button looks like this:
// LAD / FBD example (simplified)
// Network 1 - Axis enable
MC_Power (Axis := TO_Axis_1,
Enable := TRUE,
Enable_Positive := TRUE,
Enable_Negative := TRUE);
// Network 2 - Absolute move on start press
MC_MoveAbsolute (Axis := TO_Axis_1,
Execute := bStartCmd AND MC_Power.Status,
Position := 500.0, // mm
Velocity := 50.0, // mm/s
Acceleration := 100.0, // mm/s^2
Deceleration := 100.0,
Jerk := 0.0, // trapezoidal profile
Direction := 0); // shortest path
// Network 3 - Continuous read of actual position
MC_ReadActualPosition (Axis := TO_Axis_1,
Enable := TRUE,
Position := rActualPosMM,
Valid := bPosValid);
The actual position returned to the PLC is derived from the TM PTO 4's internal pulse counter. In the source manual note from Siemens Support: "Each pulse sent to the stepper motor moves it one step (forward or reverse, depending on the controller settings). So each pulse must be counted if you want to know how many steps the motor has travelled. This number of pulses (corresponding to an equal number of steps) is the value that is returned by the TM functions." Therefore the PLC's ActualPosition in user units is consistent with the pulse count as long as the mechanics (gear, leadscrew pitch) are configured correctly.
8. Open-Loop Control Without an Encoder
The most common engineering question for the TM PTO 4 is whether it can position a motor that has no encoder at all. The answer is yes, with caveats:
- The TM PTO 4 returns the commanded pulse count as the actual position. If the motor stalls due to overload, the PLC will not see a stall – it will keep reporting the position it told the drive to reach.
- For stall detection, add a simple digital input from the drive's alarm or in-position output and route it to the application. Many stepper drives expose a fault relay that closes when stall or overcurrent is detected.
- For higher integrity, install an external incremental encoder and connect it to a TM PosInput channel, or use a closed-loop stepper drive that returns a position error over its own feedback interface. The TM PTO 4 itself does not accept an encoder input.
ActualPosition as a safety-relevant value. Use it as a process value only, and place an independent safety function (e.g., a SIL-rated limit switch) at the end of every axis travel range.9. Differences Between V1.x and V2.x (the Reworked Module)
The V2.0 release corrected hardware issues and added functionality. Siemens publishes the exact change set on the support entry titled "Sales release: Version 2 of the S7-1500 TM PTO 4. 4-channel interface module for PTO (Pulse Train Output)". Always read that document before swapping a V1 module for a V2 module in a running machine – the device version selection in TIA Portal must match, and any project that hard-codes the V1 device version must be upgraded.
| Aspect | V1.x | V2.x |
|---|---|---|
| Article number | 6ES7553-1AA01-0AB0 | 6ES7553-1AA01-0AB0 (same MLFB, different firmware/hardware rev.) |
| Functional improvements | Baseline four PTO channels | Improvements detailed in the official sales release note |
| Project compatibility | Original TIA Portal device version | Requires matching device version in TIA Portal |
10. Commissioning Checklist and Verification
- Wiring audit. Verify that pulse and direction outputs of each enabled channel land on the correct pins of the drive's PTI input. Cross-wiring pulse and direction is the most common field fault.
- CPU-to-module handshake. In Online & diagnostics, confirm the TM PTO 4 reports OK with no diagnostic buffer entries.
-
Axis control panel jog. Jog the axis at low velocity in both directions. Confirm that the drive reports motion, the PLC's
ActualPositionincrements monotonically, and the direction sign matches the user's expectation. - Software limits. Configure SW limit switches in the TO. Confirm that the drive is brought to a controlled stop (not a hard stop) when the limit is reached.
- Homing sequence. Run the configured homing sequence and verify the final position value matches the mechanical reference.
- Fault injection. Trigger a drive fault (for example by stalling the motor) and confirm the application's reaction: the axis must be commanded to MC_Stop and the operator must receive a clear diagnostic message.
- Power cycle. Cycle the cabinet power. The TM PTO 4 has no absolute position memory; the application must home the axis before resuming production.
11. Troubleshooting Matrix
| Symptom | Likely cause | Remedy |
|---|---|---|
| Drive does not move at all | Pulse output wiring reversed; drive not enabled; channel not activated in module configuration | Re-check wiring against the drive manual; verify Enable in the TM PTO 4 properties; verify MC_Power.Enable is TRUE |
| Motor runs in wrong direction | DIR signal polarity inverted | Either swap DIR wiring or invert Direction in the TO configuration |
| Axis reports movement but the motor does not rotate | Pulse line shorted or open; drive set to wrong pulse-edge mode | Measure pulse output with an oscilloscope or counter; switch drive to rising-edge mode |
| Position drifts after a few moves | Mechanical slip, missed pulses due to EMI, or drive microstep setting mismatch | Reduce velocity; add shielding; align drive microstep resolution with the TO increments per motor revolution |
| CPU reports "Channel error" or module diagnostic buffer entry | Overload, short circuit, or wire break on the 24 V output | Inspect wiring and load current; clear the diagnostic and acknowledge with MC_Reset |
| V2 module not recognized after firmware change | Wrong device version selected in TIA Portal | Open device configuration, change device version to V2.x, recompile, download |
| Axis position lost after power cycle | TM PTO 4 has no absolute position memory | Home the axis at every restart; or add an absolute encoder + TM PosInput |
12. Sourcing, Spares, and Documentation Hygiene
Order the module only by its full MLFB 6ES7553-1AA01-0AB0. When stocking spares, write the firmware version on the carton. Cross-link the following two official references inside the project documentation so future engineers can find both the operating manual and the V2.0 release note without guessing:
- TM PTO 4 Technology Module (6ES7553-1AA01-0AB0) – TIA Portal manual collection
- Sales release: Version 2 of the S7-1500 TM PTO 4
FAQ
What is the article number of the S7-1500 TM PTO 4 pulse-train module?
The module's MLFB is 6ES7553-1AA01-0AB0. The same MLFB covers both the V1.x release and the reworked V2.x release; the firmware revision is selected inside TIA Portal.
Can the TM PTO 4 control a stepper drive that has no encoder?
Yes. The module counts every pulse it transmits and returns the count as the technology object's ActualPosition. Position integrity is therefore open-loop – if the motor stalls, the PLC will not see the stall unless the drive's fault output is wired back to a digital input.
Which TIA Portal technology object do I configure for a TM PTO 4 channel?
Use TO PositioningAxis and set its Drive connection to TM PTO, selecting the matching channel. This exposes the standard PLCopen MC_ blocks for absolute, relative, and velocity moves.
Does the TM PTO 4 retain its actual position after a power cycle?
No. The module has no absolute position memory. The application must home the axis after every restart, or add an external absolute encoder wired to a TM PosInput module.
Where do I find the official TM PTO 4 manual and the V2.0 release note?
The current manual entry is in the TIA Portal manual collection: TM PTO 4 Technology Module (6ES7553-1AA01-0AB0). The V2.0 release note is published at Sales release: Version 2 of the S7-1500 TM PTO 4.