PROFIdrive PZD 4-4 Telegram Structure and Word Assignment for Drives in PCS 7

In SIMATIC PCS 7, controlling variable frequency drives (such as MICROMASTER MM440 or SINAMICS G120) over PROFIBUS DP using parameter configuration 'PZD 4/4' establishes a free cyclic process data exchange of 4 words transmitted to the drive and 4 words received by the controller without parameter channel overhead. In this configuration, Output Word 1 is Control Word 1 (STW1), Word 2 is the Main Speed Setpoint (HSW, scaled where 16#4000 represents 100% rated speed), and Words 3 and 4 carry auxiliary control or torque limits. For inputs, Word 1 is Status Word 1 (ZSW1), Word 2 is Actual Speed (HIW), Word 3 is Actual Motor Current (r0027), and Word 4 conveys Actual Torque or Fault Codes.

PROFIdrive Profile Standard and PZD Communication Architecture

In industrial automation, the PROFIdrive Profile standardizes communication between automation controllers and variable speed electric drives across PROFIBUS DP and PROFINET IO networks. Communication is partitioned into two distinct functional channels:

Parameter Channel (PKW - Parameter-Kennung-Wert): Used for acyclic read/write access to drive parameters (e.g., modifying ramp-up times, motor thermal models, or controller gains). PKW consumes 4 words of bus bandwidth.
Process Data Channel (PZD - Prozessdaten): Used for deterministic, cyclic real-time control (start/stop commands, speed setpoints, drive health status, and actual current feedback). PZD words are exchanged synchronously every bus cycle.

When an engineer configures PZD 4/4 in HW Config, they deploy a 4-word input / 4-word output telegram that strips away the acyclic PKW parameter header, dedicating all bandwidth to high-speed process control.

PPO Types vs. Free Telegram PZD Configurations

Engineers frequently confuse PPO Types with PZD Telegrams:

Standard PPO Types: Defined in the legacy PROFIdrive profile. PPO 1 (4 PKW + 2 PZD), PPO 2 (4 PKW + 6 PZD), PPO 3 (0 PKW + 2 PZD), PPO 4 (0 PKW + 6 PZD), and PPO 5 (4 PKW + 10 PZD).
Free Telegram PZD 4/4 (Universal Module): PZD 4/4 is not a standard PPO type. It is a customized configuration providing exactly 4 process data words in each direction. It is functionally positioned between PPO 3 (2 PZD words) and PPO 4 (6 PZD words).
Why PZD 4/4 Is Selected in PCS 7: Standard 2-word telegrams (PPO 3) convey only command and speed, leaving no space for motor current or torque feedback. PPO 4 (6 words) consumes extra I/O memory. PZD 4/4 provides the ideal balance: control word, speed setpoint, status word, actual speed, actual current, and an auxiliary diagnostic channel.

PZD 4/4 Word Assignment and Bit Mapping Matrix

The following table details the standard word assignments and bit functions for a PZD 4/4 drive telegram in PCS 7:

Word IndexDirection: AS to Drive (Setpoint / Command)Direction: Drive to AS (Feedback / Status)Word 1 (PZD1)Control Word 1 (STW1): Bit 0: ON/OFF1, Bit 1: OFF2, Bit 3: Enable, Bit 10: Master ControlStatus Word 1 (ZSW1): Bit 0: Ready to start, Bit 2: Running, Bit 3: Fault, Bit 6: InhibitWord 2 (PZD2)Main Speed Setpoint (HSW): Scaled 0 to 16#4000 (16384 dec) = 100% rated frequencyActual Speed Feedback (HIW): Scaled 0 to 16#4000 (16384 dec) = 100% rated frequencyWord 3 (PZD3)Control Word 2 (STW2) or Torque Limit SetpointActual Motor Current (IW_ACT / r0027): Scaled percentage or raw amperesWord 4 (PZD4)Secondary Setpoint or Upper Frequency LimitActual Motor Torque (r0031) or Active Fault Code (r0947)

Step-by-Step Procedure to Configure and Interconnect PZD 4/4 in PCS 7

To configure and control an MM440 or SINAMICS drive using PZD 4/4 in PCS 7:

Configure Hardware in HW Config:
- In HW Config, insert the drive from the PROFIBUS DP catalog (e.g., SIMOVERT / MICROMASTER 4 or SINAMICS).
- Assign a valid PROFIBUS DP address (e.g., node 12).
- In the slot configuration table, insert the module: 4 Words Out / 4 Words In (PZD 4/4).
- Record the assigned peripheral input address (PIW256 to PIW262) and output address (PQW256 to PQW262).
- Save, compile, and download the hardware configuration.
Configure Drive Parameters via Drive ES or BOP/AOP:
- On the drive, configure command source: set parameter P0700 = 6 (Control via PROFIBUS DP / CB).
- Configure frequency setpoint source: set parameter P1000 = 6 (Setpoint via PROFIBUS DP / CB).
- Set telegram selection: configure parameter P0922 = 999 (Free telegram configuration with BICO).
- Map BICO feedback words: P2051.0 = 52 (ZSW1), P2051.1 = 21 (Actual frequency), P2051.2 = 27 (Actual current), P2051.3 = 31 (Actual torque).
Deploy Technological Drive Block in CFC:
- Open the CFC chart; instantiate the APL block MotSpdCL (FB1856) or Drive ES block DRVDIS.
- Connect PIW256 to the status word input, PIW258 to speed feedback PV_In, and PIW260 to motor current input.
- Connect block command outputs to PQW256 (Control Word) and scaled setpoint SP_Out to PQW258.
- Ensure bit 10 of Control Word 1 (16#0400) is forced high to assert 'Master control by PLC'.
Compile and Download S7 Program:
- Execute Chart -> Compile -> Changes Only and download changes to the controller.

Verification

Verify drive communication and operation:
1. Open the CFC chart online and monitor MotSpdCL.
2. Confirm that ZSW1 reads healthy status (16#02xx or 16#FAxx), proving communication synchronization.
3. Issue a Start command from the faceplate; confirm that bit 0 of STW1 asserts and the drive accelerates to setpoint.
4. Verify that HIW accurately reflects actual motor speed and IW_ACT displays motor amperes matching a local clamp meter.

Limitations and Operational Precautions

Control Word Bit 10 Requirement: The drive will reject all start/stop commands unless bit 10 of Control Word 1 is set to 1 ('Control requested by PLC').
Speed Normalization: Both setpoints and feedback are normalized to 16-bit integers where 16#4000 (16384 decimal) equals the drive reference frequency (P2000), NOT the maximum frequency.
Absence of PKW Channel: PZD 4/4 cannot read or modify internal drive parameters cyclically; parameter tuning must be performed acyclically via DPV1 data records (SFB52/53) or Drive ES.

Engineer FAQ

Which PPO type corresponds to PZD 4/4?

PZD 4/4 is not a standard PPO type. It is a customized free telegram module that provides 4 PZD words without the 4-word PKW parameter channel.

What scaling factor is used for speed setpoints in PZD2?

Speed setpoints use standard PROFIdrive normalization: 16#4000 hex (16384 decimal) equals 100% of the reference frequency configured in drive parameter P2000.