Wiring Siemens ET200S 1COUNT 5V Module to ABB Drive TTL Feedback

Overview

When an ABB drive exposes incremental encoder feedback on a 9-pin female D-type connector (typically labeled X7), the signals are almost always 5 V TTL differential in the form of RS-422 pairs: CHA+/CHA-, CHB+/CHB-, and CHZ+/CHZ-. A controller running an ET200S IM151-8 CPU can read this feedback, but only through a counter module that supports 5 V differential inputs. The FM350-1 is a single-width FM module designed for the S7-300 rack and will not plug into an ET200S terminal base, so it is excluded from the candidate list. The correct hardware is the SIMATIC ET200S 1COUNT 5V/500 kHz technology module (order number 6ES7 138-4DF01-0AB0). The following sections cover the signal characteristics, pin mapping, configuration, and the rationale for ruling out the FM350-1.

TTL Encoder Signal Characteristics

TTL encoder output from an ABB drive is a 5 V differential RS-422 signal, not a 24 V single-ended HTL signal. The three channels each carry an inverted pair so that the receiver can reject common-mode noise over long cable runs back to the cabinet.

ABB Drive X7 Connector Pinout

The encoder sub-D connector labelled X7 on a wide range of ABB drives (for example, ACS and ACSM families) follows the pinout listed below. Verify against the specific drive's hardware manual because pin numbering can change between firmware revisions and family members.

Siemens ET200S 1COUNT 5V/500 kHz Module

The 1COUNT 5V/500 kHz (MLFB 6ES7 138-4DF01-0AB0) is a single-channel counter module for the ET200S distributed I/O system. It accepts 5 V differential TTL/RS-422 signals, provides hardware evaluation, and supports up to 500 kHz per channel. A later variant (6ES7 138-4DF11-0AB0) extends counting to higher frequencies; check the catalog number on the side label before commissioning.

For 24 V HTL encoder feedback, use the sister module 1COUNT 24V/100 kHz (6ES7 138-4DA00-0AB0). The two modules are not interchangeable and substituting a 24 V module on a 5 V TTL encoder will produce either no counts or false triggering.

Why FM350-1 Is Not Compatible with ET200S

The FM350-1 (MLFB 6ES7 350-1AH03-0AE0 and successor variants) is a Function Module for the SIMATIC S7-300. It uses the S7-300 backplane connector and the FM-specific terminal block (40-pin). The ET200S uses the TM-E terminal base with a 20-pin front connector, and ET200S modules do not physically fit on an S7-300 rack. The ET200S IM151-8 CPU has the same S7-300 instruction set, but its local I/O bus is the ET200S "terminal module" bus, not the S7-300 P-bus. FM modules cannot be plugged into an ET200S slot.

Use the 1COUNT family of ET200S technology modules for counting, frequency measurement, and position capture inside an ET200S station. If the application genuinely requires the FM350-1 (for example, for the full 1 MHz ceiling or the SSI variant), the controller must be an S7-300 CPU with an IM360/IM361 chain or an ET200M station with PROFIBUS backplane, not an IM151-8.

ET200S IM151-8 CPU Compatibility

The IM151-8 PN/DP CPU (MLFB 6ES7 151-8AB01-0AB0 or later 6ES7 151-8AB02-0AB0) is a CPU with an integrated IM151 interface and PROFINET/PROFIBUS master capability. The 1COUNT 5V module is fully supported in the IM151-8 hardware catalog under ET200S > Technology modules > 1COUNT 5V/500 kHz. Configuration is performed in STEP 7 V5.5 with the ET200S HSP, or in TIA Portal V13+ with the ET200S HSP installed.

Wiring Diagram: ABB X7 to 1COUNT 5V Module

The following table maps the ABB X7 encoder pins to the 1COUNT 5V/500 kHz front connector (20-pin). Signal names follow the Siemens manual: 1A, 1A-, 1B, 1B-, 1Z, 1Z-, and 1GND for channel 1. Use a shielded twisted-pair cable, ground the shield at the cabinet entry only, and tie the digital grounds (drive pin 5 to module pin 6) at a single point to avoid ground loops.

Configuring the 1COUNT 5V in STEP 7 / TIA Portal

1. Install the ET200S hardware support package (HSP) for your STEP 7 or TIA Portal version. The 1COUNT 5V/500 kHz appears under ET200S > Technology modules.
2. Drag the 1COUNT 5V/500 kHz into the ET200S station next to the IM151-8 CPU. The slot is a TM-E (15 mm) terminal base.
3. Open the module's properties and set:
   • Operating mode: Continuous counting for an encoder, or Single counting with gate if you need a start/stop control.
   • Signal evaluation: Single (1×) for quadrature ×1, Double (2×) for ×2, or Quadruple (4×) for ×4 — ABB drives default to 5 V TTL with ×4 decoding at 500 kHz per channel.
   • Encoder type: 5 V TTL symmetric (RS-422).
   • Hardware interrupt at Z: enable if you need a marker / homing pulse.
   • Load value / end value: set the upper count limit if you want the counter to wrap.
4. Assign the input addresses (default: input bytes starting at the next free slot). The status word is the first two input bytes; the count value occupies the next four input bytes.
5. Compile and download the hardware configuration. The module's SF LED should extinguish after a successful download.

Reading the Counter in the IM151-8 User Program

For a basic OB1 read, use the standard library block FC0 "CNT_CTL1" from the ET200S Technology Module library, or read the I/O directly in the symbol table. The 32-bit count value is little-endian and can be moved into a DINT tag.

// Read raw 32-bit count value (LAD/FBD equivalent shown as STL for IM151-8)
LAR1  P##Input_Addr          // pointer to I/O area
L     ID [AR1,P#0.0]         // load 4 bytes from the count slot
T     "Counter_DB".Count     // store to DB
// Check status word for hardware error
L     IW [AR1,P#0.0]         // load status word
L     W#16#0004              // mask "hardware fault" bit
==I
S     "Counter_DB".HW_Fault

Step Output Module Alternatives for 5 V

The original question also asked whether ET200S offers a 5 V step / pulse output module to drive a stepper input. The 1COUNT 5V module provides two 24 V digital outputs (DQ0 and DQ1), which can be used for cam switching or a PTO at low frequency, but the 1COUNT 5V/500 kHz is not a 1 MHz step output.

Verification and Commissioning

1. Power up the ET200S station. The SF LED on the 1COUNT 5V module must be OFF and the RUN LED must be solid green.
2. Force a small shaft rotation on the ABB drive. Monitor the count value in a watch table; it should advance monotonically in the configured sign convention.
3. Reverse the shaft direction and confirm the count value changes sign if "invert direction" is enabled in the module's properties.
4. Trigger a Z event by rotating past the index mark. The hardware-interrupt OB (for example OB40 on IM151-8) should fire once per revolution.
5. Connect an oscilloscope to pins 1 (CHA+) and 6 (CHA-) at the module front connector. Verify a clean 5 V differential pair with a 90° quadrature offset to channel B.
6. Run a continuous counting test for ten minutes at the drive's maximum speed and confirm no count jumps, dropouts, or status-word errors.

Troubleshooting Matrix

Field-Proven Cautions

• Never route the encoder cable parallel to VFD output conductors. ABB X7 TTL is balanced but capacitive coupling can still push common-mode voltage past the 7 V receiver common-mode range of the 1COUNT 5V module.
• Keep the shield continuous from the drive sub-D to the module front connector, but ground it at the cabinet entry gland only. A shield landed at both ends creates a ground loop and is the leading cause of TTL count jitter in field installations.
• If the drive is sourcing TTL but the count is unstable, swap the encoder cable before suspecting the module. A broken twisted pair in the shield often shows up as a single missing edge rather than a complete failure.
• The 1COUNT 5V/500 kHz has a single count channel. If the application needs two independent counters (for example, A and B axis), use two 1COUNT modules rather than multiplexing on a 2COUNT variant that does not exist in the ET200S catalog.

Summary of the Hardware Decision

For a single-channel 5 V TTL incremental encoder from an ABB drive wired into an ET200S IM151-8 station, the 1COUNT 5V/500 kHz (6ES7 138-4DF01-0AB0) is the correct module. The FM350-1 is rejected because it belongs to the S7-300 family and cannot be installed in an ET200S rack. Wire the six TTL pairs (A, A-, B, B-, Z, Z-) plus a single-point digital ground from the X7 connector to the module's 20-pin front connector using a shielded twisted-pair cable, configure the module as RS-422 symmetric with ×4 evaluation if the drive parameter is set to quadrature ×4, and verify the count value with an oscilloscope during commissioning.