Configuring CPU 314C-2DP Pulse Train Output for Panasonic Servo

Overview: Pulse Train Command of a Panasonic Servo from an S7-300 CPU 314C-2DP

The application described in this article pairs a Siemens SIMATIC S7-300 CPU 314C-2DP (order number 6ES7 314-6CH04-0AB0) with a Panasonic MINAS-series servo drive (MBDJT2210, 220 V class) using the integrated pulse-train output of the CPU. Because the CPU 31xC family embeds technology functions on the back of the PLC, no FM 351/FM 352/FM 353 positioning module is required for a basic point-to-point move; the work is split between STEP 7 / HW Config (declaring the integrated channel as PTO/PWM), SFB 49 (runtime pulse-width modulation), and the Panasonic drive's Pr parameters (defining pulse input shape and motor response).

This reference covers hardware configuration, signal wiring, parameter setup on the drive side, SFB 49 programming, verification, and a troubleshooting matrix for the common faults observed during commissioning.

Prerequisites

System Architecture

The CPU 314C-2DP exposes two channels of technology I/O on its front connector X1 (40-pin sub-D). The channels can be configured individually as:

• Digital input (with optional interrupt, filter, latch, frequency measurement)
• Digital output (with optional PWM, frequency output, or pulse-train output)
• Counting / positioning channel

For a Panasonic MBDJT2210 in pulse + direction command mode, the CPU's integrated DO channel is configured as a pulse-train output. The drive receives differential signals (PULSE, /PULSE, SIGN, /SIGN) on connector X4 of the drive. Direction is conveyed by the SIGN line level; distance is conveyed by the number of pulses.

CPU 314C-2DP Hardware Configuration

1. Open the S7 project in STEP 7 and insert the CPU 314C-2DP from the hardware catalog (SIMATIC 300 > CPU 300 > CPU 314C-2DP > 6ES7 314-6CH04-0AB0 > V3.x).
2. Open HW Config and double-click the CPU to expose the object properties.
3. Select the "Integrated I/O" tab.
4. For each of the four channels used (DO0..DO3), assign the function "Pulse-train output / PWM".
5. Switch to the "Technology" tab of the CPU properties. Enable the channel used (typically Channel 0 for DO0/DO1 and Channel 1 for DO2/DO3).
6. Set Pulse output mode = Pulse + Direction (this matches Panasonic Pr 0.05).
7. Set Output format = Pulse/direction, positive logic unless drive is wired for negative logic.
8. Download the hardware configuration to the PLC (PLC > Download to Target).

Panasonic MBDJT2210 Servo Drive Parameter Setup

The Panasonic MINAS A4 / MBDJT series uses Pr-class parameters accessed from the front-panel keys or via PANATERM. The relevant subset for pulse-train command is:

The electronic gear ratio (Pr 0.08 / Pr 0.09) sets how many motor shaft revolutions correspond to one motor encoder turn. For a 2500-line encoder with 4x decoding, one motor revolution = 10000 pulses. To command 1 motor revolution per 1000 pulses from the PLC, set Pr 0.08 = 1000 and Pr 0.09 = 10000.

Wiring and Signal Interface

The CPU 314C-2DP integrated digital outputs are 24 V sourcing (active high). The Panasonic MBDJT2210 accepts 24 V single-ended or 5 V differential line driver inputs on connector X4. For noise immunity above 50 kpps, use the differential driver output by sourcing an external 26LS31-type line driver between the CPU outputs and the drive inputs. Pinout reference:

SFB 49 PWM Function Block

SFB 49 ("PULSEGEN" / "PWM") is part of the technology FB library for the S7-300 C-CPUs. It modulates the configured output channel with a fixed period and adjustable duty cycle. Calling SFB 49 in OB1 cyclically updates the PWM ratio and can be combined with a stepper-driven counter for true pulse-train output if a position profile is required.

SFB 49 Interface (simplified)

Ladder Example (S7-300, FBD/equivalent)

// OB1 - cycle at OB1 priority class
// Allocate instance DB once: DB49 "PWM_DB49"

      CALL  "PULSEGEN" , DB49
      LADDR      := W#16#0300      // base address of integrated DO0/1
      SW_ENABLE  := M10.0          // operator enable
      OUT_FEEDBACK:= I124.0         // drive RDY contact (optional)
      PERIOD_CV  := MW20            // period in 0.1 ms e.g. 1000 = 100 ms
      PULSE_CV   := MW22            // duty e.g. 500 = 50 %
      PERIOD     := MW24
      PULSE      := MW26
      STS_C_FG   := M10.1
      STS_C_ST   := M10.2
      ERROR      := MW28
      ERR_CODE   := MW30

For a true PTO profile with acceleration ramp, use the integrated positioning channel configured as "Axis" in HW Config and call SFB 47 ("POS") instead of SFB 49. The 314C-2DP supports up to one positioning axis and one counting channel.

Period and Frequency Conversion

The CPU 31xC integrated PWM channels have a fixed resolution. The Siemens manual specifies:

Frequency and duty relationship for SFB 49:

f_out [Hz] = 1 / (PERIOD × 100 µs)
duty [%]  = (PULSE_CV / PERIOD_CV) × 100
Max command freq of MBDJT2210 = 500 kpps (Pr 3.16)

If your application requires frequencies above the integrated PWM ceiling of 10 kHz, step up to one of the following options:

• FM 351 (single-axis positioning module) - up to 200 kHz
• FM 353 (high-speed stepping) - up to 2 MHz
• FM 354 (servo positioning) - up to 1 MHz, closed-loop via incremental encoder

Commissioning Procedure

1. Power down the drive. Verify mains (220 V L/N/PE) and 24 V DC logic supply to the CPU.
2. Connect an oscilloscope or signal analyzer to pins 3/4 (PULSE) of the MBDJT2210.
3. In STEP 7, place a watch table on MW20 (PERIOD) and MW22 (PULSE_CV). Set SW_ENABLE = TRUE.
4. Start with PERIOD = 1000 (100 ms, 10 Hz) and PULSE = 500 (50 % duty). Confirm pulses on scope.
5. On the drive, enter the trial run mode: Pr 6.05 = 0 to disable trial-run inhibit; drive display should read "drE" (drive ready).
6. Set Pr 6.00 = 1 (JOG mode). Motor should move at the speed dictated by the PWM frequency divided by the electronic gear.
7. If the motor does not move, verify the SON (Servo-On) input on the drive is energized (typically SI0 closed, +24 V on pin 29 of X4).
8. Once steady operation is verified at low speed, ramp the period down to drive the machine toward the desired speed, but never below PERIOD = 100 (= 10 µs = 100 Hz).
9. Save drive parameters and back up the S7 project.

Verification Checklist

Troubleshooting Matrix

Edge Cases and Field Tips

PTO vs PWM. A 100 % duty cycle from SFB 49 holds the output high without toggling - this is not a continuous pulse train. For servo positioning where the number of pulses defines distance, use SFB 47 with a positioning DB, or use the integrated axis in HW Config.

Mechanical inertia. The integrated PTO channel does not include S-curve or jerk limiting. For high-inertia loads, generate the ramp in the application code (trapezoidal velocity profile in OB35) and feed the instantaneous frequency to the PWM input.

EMI on long cables. For cable runs over 10 m, use a 26LS31 line driver and 26LS32 line receiver at the drive side. Set Pr 0.07 = 0 and avoid shielded twisted pair rated below 100 MHz.

Multi-axis scaling. The CPU 314C-2DP has only one integrated positioning channel. To control a second MBDJT2210, add an FM 354 to the rack; STEP 7 will treat it as a standalone axis on the PROFIBUS side.

Backup. Export the drive parameter set with PANATERM after each change; the CPU project (.s7p) does not include drive parameters.

FAQ

References and Standards

• S7-300 CPU 31xC Technological Functions Manual - source of SFB 49 interface, frequency range, and timing diagrams.
• CPU 314C-2DP (6ES7 314-6CH04-0AB0) Manual - I/O base addresses and module diagnostics.
• Industrial motion control portfolio - alternative servo hardware reference for cross-platform migration considerations.
• Panasonic MINAS A4-series Technical Reference for MBDJT2210 Pr parameter layout (drive-side documentation supplied with the drive).
• IEC 61131-3 - programmable controller programming languages referenced in STEP 7 (IEC FB and LAD/FBD/ST equivalents).