Configuring 1SI 5V/500kHz Counter Module on S7-300 ET 200S

Module Identification and System Architecture

The Siemens 1SI 5V/500kHz counter module (MLFB 6ES7 138-4DE02-0AB0) is a single-channel incremental encoder/counter module designed for the ET 200S distributed I/O system. It accepts 5V TTL differential (RS-422) pulse trains at input frequencies up to 500 kHz, evaluates the A/B quadrature signals, and returns a 32-bit count value, status flags, and a hardware gate state to the host PLC. The module is the standard choice when the encoder signal is 5V TTL and the application requires high count rates, precise position capture, or direct load-signal evaluation.

Within an ET 200S station, the 1SI 5V/500kHz electronics module must be inserted into a TM-E 30S terminal module family. The variant TM-E 30S-44-01 (6ES7 193-4CG40-0AA0) provides the 30 mm wide screw-type terminals and the internal wiring path that maps the encoder signals (A, /A, B, /B, N, /N, 24V encoder supply) to the front connector of the electronics module. The terminal module is the only piece of the station that physically exposes the encoder lines; the electronics module itself is replaced during service without re-wiring.

For an S7-300 station based on a CPU 315-2PN/DP (MLFB 6ES7 315-2EH14-0AB0), the ET 200S head-end is selected according to the fieldbus used:

• PROFIBUS DP — IM 151-1 STANDARD (6ES7 151-1AA05-0AB0) or IM 151-1 HF (6ES7 151-1BA02-0AB0)
• PROFINET — IM 151-3PN HF (6ES7 151-3BA23-0AB0) for 1SI 5V/500kHz, since the standard IM 151-3PN does not support 1SI modules

The IM 151-3PN HF is required because the 1SI 5V/500kHz uses the technological-functions record set that is only available on HF interface modules. A CPU 315-2PN/DP host on PROFINET integrates the ET 200S station through a standard GSD file (GSDML-Vx.x-Siemens-ET200S-xxxxxxxx.xml) imported into the device catalog.

Technical Specifications of 1SI 5V/500kHz

The following electrical and functional data are taken from the Siemens "ET 200S Technological Functions" manual, which lists this module under part number 6ES7 138-4DE02-0AB0.

Prerequisites

Before commissioning the counter module, verify the following:

1. STEP 7 V5.5 SP4+ (Classic) or TIA Portal V13+ — Both support the 1SI 5V/500kHz via the HSP (Hardware Support Package) GSD files. In STEP 7 Classic, install HSP "ET200S_AI_AO_DI_DO_1SI" or the cumulative HSP for the 138-4DE02 module.
2. GSD/GSDML file — Import the matching GSDML for the IM 151-3PN HF and the 1SI 5V/500kHz sub-module into the device catalog.
3. IM 151-3PN HF — Required for PROFINET integration with the 1SI 5V/500kHz, since the standard IM 151-3PN does not support the technological-functions record set.
4. 5V TTL encoder — The encoder must be a true 5V differential (RS-422) output device, not a 24V HTL push-pull device. Confirm via encoder datasheet that the high-level output voltage is between 2.0V and 5.5V and that the line driver is RS-422 compatible (e.g., 26LS31, AM26C31).
5. Shielded twisted-pair cable — Use a shielded twisted-pair cable with one pair per channel (A/̄Ā, B/̄B̄, N/̄N̄) and connect the shield to the functional earth terminal of the TM-E 30S-44-01 at the cabinet entry only.
6. PROFINET/PROFIBUS configuration tool — For the CPU 315-2PN/DP, use either SIMATIC Manager (STEP 7 V5.5) or TIA Portal. The article below covers STEP 7 Classic first and notes the TIA Portal differences at the end.

Hardware Configuration in STEP 7 (HW Config)

1. Open the S7 project in SIMATIC Manager and launch HW Config.
2. Insert the CPU 315-2PN/DP (6ES7 315-2EH14-0AB0) into slot 2 of the S7-300 rack.
3. Open the PROFINET subnet on the CPU and drag the IM 151-3PN HF (6ES7 151-3BA23-0AB0) onto the subnet. Assign a PROFINET device name (e.g., "et200s-cntr1") and an IP address in the same subnet as the CPU.
4. In the IM 151-3PN HF slot table, insert the 1SI 5V/500kHz module (6ES7 138-4DE02-0AB0) at the next free slot. The slot is automatically mapped to a TM-E 30S-44-01 terminal module.
5. Double-click the 1SI module to open its properties. Configure the following parameters:
   • Operating mode: "Continuous counting up/down" for an A/B encoder with direction discrimination
   • Signal evaluation: "4-fold evaluation" (quadrature 4×) for maximum resolution
   • Counter range: −2,147,483,648 to 2,147,483,647 (32-bit signed)
   • Hardware gate: "interrupted, cancels the count" or "interrupted, stops the count" depending on application
   • Software gate: "Cancel with "0"" (default)
   • Encoder monitoring: enable wire break and signal-level diagnostics
   • Comparator DQ0 / DQ1: enable and assign comparison value via control interface
6. Click "OK" and download the HW Config to the CPU. The configured I/O addresses are displayed in the slot table — for example, inputs starting at PIW 288 and outputs starting at PQW 288. Note these addresses for the user program.

TM-E 30S-44-01 Terminal Assignment

The terminal module exposes the following screw terminals. The pinout below is the standard mapping for the 1SI 5V/500kHz electronics module; always verify against the wiring diagram printed inside the terminal module door before commissioning.

For the support entry describing the wiring diagram and an example project, refer to the Siemens support article ID 45977588 in the Siemens Industry Online Support portal. The example project demonstrates the IM 151-3PN configuration and a sample STEP 7 program for the 1SI 5V/500kHz module.

Encoder Signal Level Considerations

The 1SI 5V/500kHz module is unusual in the Siemens product line because most ET 200S counter modules (1SI 24V/100kHz, 1COUNT 24V/100kHz, 1SSI) accept 24V signals. The 5V variant is purpose-built for high-frequency applications where 5V TTL encoders are still common — typically small incremental encoders with resolutions above 5,000 ppr (pulses per revolution) running at shaft speeds that push the input frequency above 100 kHz.

The 5V TTL encoder inputs accept a true differential RS-422 signal with the following threshold limits:

• V_IH (differential high) ≥ 200 mV
• V_IL (differential low) ≤ −200 mV
• Common-mode input range ±7V

A 24V HTL encoder output (typical high level: 22 to 26V) will fail the V_IH/V_IL thresholds and the module reports a wire break. The recommended solutions are:

1. Use a true 5V TTL encoder — common in the 1,000–10,000 ppr range with 5V supply from the module. Manufacturers: Hohner, Kübler, Baumer, Sick, Heidenhain (E-series with TTL option).
2. Use a 24V-to-5V level converter — Siemens does not sell a dedicated HTL-to-TTL converter for ET 200S. Third-party modules (e.g., Phoenix Contact MINI MCR-2-UI-REL or Wieland TTL converter) are used; verify the converter bandwidth is at least 10× the maximum input frequency to preserve edge fidelity at 500 kHz.
3. Use a 24V counter module instead — 1SI 24V/100kHz (6ES7 138-4DE11-0AB0) or 1COUNT 24V/100kHz (6ES7 138-4DL00-0AB0). The frequency limit drops to 100 kHz, which is sufficient for many applications.

Operating Modes

The 1SI 5V/500kHz supports four primary operating modes, selected in HW Config:

For position-control applications with a single A/B encoder, "Continuous counting, up/down" with 4-fold evaluation gives the maximum resolution (4 × pulses-per-revolution counts per shaft turn).

Address Map and I/O Access

The 1SI 5V/500kHz occupies 8 bytes of input and 8 bytes of output process image. The default base addresses depend on the slot and the IM 151-3PN HF configuration. A typical mapping (PROFINET slot 1) is:

The status word (PIW 288) is decoded as follows:

The control word (PQW 288) is decoded as:

Sample Program — Up/Down Counting on S7-300 (STEP 7 Classic, STL)

The following sample is taken from the "ET 200S Technological Functions" manual (page 121 and following) and adapted to a standalone OB1 cycle without the higher-level FCs from the Siemens library. It is the minimum program required to:

1. Open the software gate
2. Read the current count and direction
3. Set the counter to a load value (e.g., 0) on a button press
4. Acknowledge the comparator outputs

Data block DB100 layout:

DATA_BLOCK DB100
  STRUCT
    iCount   : DINT ; // current count (copy of PID 292)
    iStatus  : WORD ; // copy of PIW 288
    iLoadVal : DINT ; // load value = 0
    bGate    : BOOL ; // software gate request
    bSetZero : BOOL ; // "Set to zero" pushbutton
    bCmp0Ack : BOOL ; // comparator 0 acknowledge
    bCmp1Ack : BOOL ; // comparator 1 acknowledge
    bDir     : BOOL ; // up/down direction (TRUE = up)
    bRunning : BOOL ; // gate open flag
  END_STRUCT
END_DATA_BLOCK

OB1 — main cyclic program (STL, comments inline):

// ----- READ INPUTS -----
L     PIW 288            // status word
T     DB100.DBW  2       // DB100.iStatus
L     PID 292            // 32-bit count value
T     DB100.DBD  0       // DB100.iCount

// ----- DECODE DIRECTION -----
A     DB100.DBX   3.1    // STS_DIR bit (bit 1 of status word)
=     DB100.DBX  12.0    // DB100.bDir

// ----- SOFTWARE GATE HANDLING -----
A     DB100.DBX   8.0    // DB100.bGate from HMI / logic
=     Q 288.0            // CTRL_SW_GATE bit (bit 0 of PQW 288)

// ----- SET COUNTER TO LOAD VALUE ON REQUEST -----
A     DB100.DBX   8.1    // DB100.bSetZero (pushbutton)
FP                         // rising-edge detect
S     Q 288.1            // CTRL_SET bit (bit 1 of PQW 288)
A     DB100.DBX   8.1
FN                         // falling-edge detect
R     Q 288.1            // release CTRL_SET

// ----- WRITE LOAD VALUE -----
L     DB100.DBD  12      // DB100.iLoadVal
T     PQD 292            // load value (32-bit)

// ----- COMPARATOR ACKNOWLEDGE -----
A     DB100.DBX   8.2    // DB100.bCmp0Ack
S     Q 288.8            // CTRL_CMP0_ACK (bit 8 of PQW 288)
A     DB100.DBX   8.2
R     Q 288.8

A     DB100.DBX   8.3    // DB100.bCmp1Ack
S     Q 288.9            // CTRL_CMP1_ACK (bit 9 of PQW 288)
A     DB100.DBX   8.3
R     Q 288.9

The same program in TIA Portal SCL is shorter and easier to maintain:

// Counter: 1SI 5V/500kHz, slot 1, base address 288
// Hardware identifier (HW ID) is read from the device configuration
// 'hwCnt' is the HW ID of the 1SI module

// 1. Read process image (PI service is implicit in TIA Portal)
iStatus  := "CNT_IN".STS;        // alias for PQW 288 input area
iCount   := "CNT_IN".COUNT;     // alias for PID 292

// 2. Decode direction
bDir := (iStatus AND 16#0002) <> 0;   // bit 1 = STS_DIR

// 3. Open software gate
IF bGateRequest THEN
    "CNT_OUT".CTRL := "CNT_OUT".CTRL OR 16#0001;   // CTRL_SW_GATE
ELSE
    "CNT_OUT".CTRL := "CNT_OUT".CTRL AND 16#FFFE;
END_IF;

// 4. Set counter to load value on rising edge
IF bSetZero AND NOT bSetZeroOld THEN
    "CNT_OUT".CTRL := "CNT_OUT".CTRL OR 16#0002;   // CTRL_SET
ELSE
    "CNT_OUT".CTRL := "CNT_OUT".CTRL AND 16#FFFD;
END_IF;
bSetZeroOld := bSetZero;

// 5. Write load value
"CNT_OUT".LOAD := iLoadVal;          // 32-bit DINT

// 6. Comparator acknowledge
IF bCmp0Ack THEN
    "CNT_OUT".CTRL := "CNT_OUT".CTRL OR 16#0100;   // bit 8
ELSE
    "CNT_OUT".CTRL := "CNT_OUT".CTRL AND 16#FEFF;
END_IF;

Comparator Configuration for Up/Down Position Control

To use the hardware comparators for position control, the comparison value is written to a separate I/O range, not the load value range. The address for the comparator setpoint depends on the slot. The typical layout on PROFINET slot 1 is:

The comparator mode is configured in HW Config (Properties → 1SI module → Comparator). For a position switch (e.g., "position reached at 5,000 counts"), enable the comparator in "Single" mode and load the setpoint:

L     5000
T     PQD 296            // comparator 0 setpoint
SET
=     Q 288.3            // CTRL_CMP0_EN (bit 3 of PQW 288)
R     Q 288.3

When the counter reaches 5,000, STS_CMP0 (bit 2 of PIW 288) is set, the corresponding digital output DQ0 (terminal 11) switches high, and the STS_CMP0 bit stays set until the user program writes CTRL_CMP0_ACK (bit 8) high to acknowledge.

Commissioning and Verification

1. Power the ET 200S station. The IM 151-3PN HF BUS-FAULT LED should be off and the RUN LED on the CPU should be steady green.
2. From the STEP 7 / TIA Portal online view, force Q 288.0 = 1 (open software gate). The status word PIW 288 bit 0 (STS_GATE) should change to 1 within one DP/PN cycle.
3. Connect an oscilloscope or signal generator to terminals 1/2 of the TM-E 30S-44-01 and inject a 5V TTL square wave at 1 kHz on track A only (terminals 1 and 2, differential). The count value (PID 292) should increment at 1,000 counts per second.
4. Inject a 1 kHz quadrature signal (A leading B) on terminals 1/2 and 3/4. The count should still increment; the direction bit (PIW 288 bit 1) should read 1. Reverse B (swap terminals 3 and 4) and the direction bit should read 0 while the count decrements.
5. Inject a 500 kHz signal at the rated amplitude. The count should follow with a 4× evaluation (4,000 counts per mechanical pulse). If the count skips, the cable is too long or the encoder is bandwidth-limited; shorten the cable or check the encoder datasheet.
6. Trigger a wire break by disconnecting the /A line (terminal 2). The DIAG LED on the module should flash red and STS_DIAG (PIW 288 bit 7) should go high. Reconnect and the diagnostic clears on the next PN cycle.
7. Toggle the hardware gate (terminal 9 to 24V) and verify the count freezes. The hardware gate has higher priority than the software gate.

Troubleshooting Matrix

Differences in TIA Portal

For projects migrated to TIA Portal V13 or later, the configuration steps are equivalent but the UI differences are:

1. The 1SI module is added from the device catalog under "ET 200S → IM 151-3PN HF → Counter → 1SI 5V/500kHz".
2. Process image names (e.g., "CNT_IN", "CNT_OUT") are defined in the PLC tags and are symbolic — the absolute address (PIW 288) is shown on the right of the tag editor for cross-reference.
3. The hardware identifier (HW ID) is used by the I/O read/write blocks (e.g., RDREC, WRREC for record-set access to comparator configuration). TIA Portal generates the HW ID automatically.
4. The Technological Functions library (FC "CNTR_1SI") is included from "Options → Support Packages → SIMATIC ET 200S Tech Functions" if a higher-level FC interface is required.

Safety and Maintenance Notes

• Disconnect the ET 200S station power before replacing the 1SI electronics module. The module can be hot-swapped only when the IM 151 interface module and the station configuration explicitly support module replacement in RUN (CiR); the standard ET 200S configuration requires a STOP state for module exchange.
• After replacement, the 1SI 5V/500kHz returns the count to zero unless the load value is re-written by the user program. Include the load-value write in OB100 (restart) or OB1 to ensure deterministic position recovery after a module swap.
• The encoder cable shield must be terminated at the TM-E functional earth terminal (terminal 13) using a short pigtail (≤ 50 mm) to avoid pigtail-induced EMI at 500 kHz.
• Do not route the encoder cable parallel to VFD output cables or to DC high-current busbars. A separation of at least 200 mm, or a metal divider, is recommended for 5V TTL signals at 500 kHz.

FAQ