Configuring S7-400H to Yokogawa CS3000 via PROFIBUS DP

Integration Overview

Interfacing a Siemens SIMATIC S7-400H redundant controller with a Yokogawa CENTUM CS 3000 distributed control system over PROFIBUS DP is a common requirement in hybrid plants where Siemens PLC subsystems handle discrete/batch interlocks and Yokogawa DCS layers handle continuous regulatory control. The CPU 414-4H (order number 6ES7 414-4HJ04-0AB0) ships with an integrated PROFIBUS DP interface (IF1, MPI/DP) that can be configured as a DP Master (Class 1) per EN 50170. Yokogawa's CENTUM CS 3000, built on the Windows NT operation/monitoring platform, supports PROFIBUS DP through dedicated field control station modules.

The core architectural problem is that both controllers want to be DP Masters - the S7-414-4H CPU is a DP Master by default and the Yokogawa PROFIBUS interface module is also a DP Master. A PROFIBUS segment allows exactly one active Class 1 master, so the two masters must be coupled through a DP/DP Link coupler rather than connected to a common bus. The coupler isolates the two masters, replicates the input image from one side into the output image of the other, and provides galvanic isolation between the segments.

System Components and Prerequisites

PROFIBUS DP Master-to-Master Architecture

PROFIBUS DP defines three device classes: DP Master Class 1 (DPM1), DP Master Class 2 (DPM2, used for configuration/diagnostics), and DP Slave. In a single segment, only one DPM1 may be active at a time. When two controllers must exchange data, three viable topologies exist:

1. Single-master, single-slave: One controller is DPM1, the other is a DP slave. Both retain the role asymmetry; one cannot be a master on its own bus. Not applicable here because both sides are designed as masters.
2. DP/DP Link coupler (recommended): Each side sees the coupler as a slave on its own segment. The coupler buffers up to 244 input and 244 output bytes per direction and mirrors them across the two electrically isolated segments. Each side retains its full master status on its own bus and is unaware of the topology beyond the link.
3. Direct master-master via FMS/FDL: Historically possible with FMS services, but FMS is largely deprecated in favor of DP and is not supported by the S7-414-4H integrated DP port.

The DP/DP Link is the only solution that preserves native DP behavior on both sides and works with the standard Yokogawa PROFIBUS module.

DP/DP Link Coupler Selection and Wiring

The Siemens DP/DP Link (e.g., 6ES7 158-0AD01-0XA0) is a standalone DIN-rail module. It contains two electrically isolated DP interfaces (X1 and X2), each presenting as a DP slave to the connected master. Configuration is performed via the DIP switches on the front of the device - no programming tool is required. The total transfer capacity is 244 input bytes and 244 output bytes per direction. Data is mirrored from the inputs of one segment to the outputs of the other and vice versa.

Wiring Topology

Connect the S7-414-4H X1 (DP) port to the DP/DP Link's X1 (or X2 - the link's two ports are identical). Connect the Yokogawa ALP121 PROFIBUS port to the other DP/DP Link port. Enable terminating resistors only at the two physical line ends (one per segment). The DP/DP Link supplies internal bus termination if the segment is short and only the coupler is on that segment, but in practice the S7-400 and Yokogawa module remain the line ends, and the link sits in the middle with termination off.

STEP 7 Hardware Configuration

Step 1 - Configure the S7-414-4H DP interface

Open the SIMATIC Manager, load the S7-400H station, and open HW Config. Double-click the CPU 414-4H, select the DP tab, and click Properties on the integrated DP interface. Configure:

• Interface: PROFIBUS
• Address: e.g. 2 (must be unique on the segment)
• Subnet: Create a new PROFIBUS subnet, e.g. "PROFIBUS(1)"
• Highest PROFIBUS address: 126 (default)
• Profile: DP
• Mode: DP Master

Step 2 - Add the DP/DP Link as a slave

In the PROFIBUS DP catalog, expand Additional Field Devices > Gateway > DP/DP Link. Drag the DP/DP Link onto the PROFIBUS(1) subnet. Assign it slave address 3 (any unused address). Right-click the link symbol, open Properties > DP Slave Configuration, and define the slot mapping. Each slot corresponds to one byte of input and one byte of output as seen from the S7-414-4H side.

Step 3 - Configure slot consistency

Critical decision: how much data per slot and at what consistency level.

Rule: If any data block exceeds 4 bytes, or if a block is 3 bytes, the read/write must use SFC14 (DPRD_DAT) for reading and SFC15 (DPWR_DAT) for writing. These block transfers handle the consistency over the entire DP cycle. Reading and writing the process image directly (L PIW / T PQW) only works for byte/word/dword up to 4 bytes and is consistent within the OB1 scan only when the data fits into a single I/O update.

GSD File Installation and Slot Mapping

For the Yokogawa side, obtain the GSD file shipped with the ALP121 module (Yokogawa typically provides it on the installation DVD or the Yokogawa download portal). In HW Config, choose Options > Install GSD File and select the file. The Yokogawa module then appears in the catalog under PROFIBUS DP > Other Field Devices > Yokogawa. The GSD describes the available I/O modules (digital in/out, analog in/out) and their consistency behavior.

SFC14/15 Consistent Data Programming

For slot data larger than 4 bytes (or equal to 3), use the standard SFCs in OB1 or a dedicated OB (for time-critical data, OB35 at 100 ms is common).

Reading from the Yokogawa side (inputs from DP/DP Link)

// STL example - read 32 bytes of consistent data
// LADDR  = I/O start address from HW Config (e.g. 256)
// RET_VAL= error code returned by SFC
// RECORD = destination DB area (must match length)

CALL  "DPRD_DAT"
     LADDR  := W#16#100      // 256 decimal, from HW Config slot 0
     RET_VAL := MW100        // 0 = OK; see error table below
     RECORD := P#DB20.DBX0.0 BYTE 32

// Evaluate RET_VAL
L     MW100
L     0
==I
JC    ok
// non-zero: see SFC14 error code table
ok: NOP 0

Writing to the Yokogawa side (outputs to DP/DP Link)

CALL  "DPWR_DAT"
     LADDR  := W#16#110      // 272 decimal, outputs from HW Config
     RECORD := P#DB21.DBX0.0 BYTE 32
     RET_VAL := MW102

Structured Text (SCL) alternative

// FB block-style wrapper - call in OB1
IF #bInit THEN
   #iStatusRead := DPRD_DAT(LADDR := #wInAddr,
                            RECORD := #tRxArea);
   #iStatusWrite := DPWR_DAT(LADDR := #wOutAddr,
                             RECORD := #tTxArea);
END_IF;

// Common pattern: re-trigger every OB1 pass for steady exchange
DPRD_DAT(LADDR := 16#100, RET_VAL := #iStatusRead, RECORD := #tRxArea);
DPWR_DAT(LADDR := 16#110, RET_VAL := #iStatusWrite, RECORD := #tTxArea);

SFC14/15 RET_VAL error codes

Bus Parameter Calculation

When two masters are coupled via a DP/DP Link, each segment is independent - baud rate, slot time, and rotation time can differ between them. The link buffers and re-issues frames, so a slow Yokogawa segment (e.g. 1.5 Mbit/s) and a fast Siemens segment (e.g. 12 Mbit/s) coexist without issue. However, each segment must be tuned to its own set of slaves.

Key parameters (set in HW Config > Properties > PROFIBUS > Network Settings)

Tbit at 1.5 Mbit/s = 0.667 µs. Tbit at 12 Mbit/s = 0.0833 µs. For each additional slave, the cycle time grows by approximately the slot time plus the telegram length. Use the bus parameter diagnostic in HW Config (PROFIBUS > Bus Diagnostics) to verify the calculated cycle time stays well below the CPU scan time (a 100 ms cycle budget leaves generous margin).

Yokogawa CENTUM CS 3000 PROFIBUS Setup

On the Yokogawa side, the PROFIBUS module is configured inside the CENTUM Builder engineering tool. The CS 3000 architecture is built on Windows NT for HMI components and the VP/NP station for operation/monitoring; the PROFIBUS master module resides in the field control station (FCS) and acts as a Class 1 DP master over its segment. Reference the Yokogawa technical report on the CS 3000 system architecture for the overall network topology and the Yokogawa Technical Information TI33Q01B10-01E for migration and field controller details.

1. Create a PROFIBUS subnet in CENTUM Builder matching the physical segment.
2. Insert the DP/DP Link as a Yokogawa-side slave (address must match the address set on the link's DIP switches and the address set in STEP 7 - they are different addresses on the two segments, but the link is one device, not two).
3. Define input and output modules in the Yokogawa configuration with the same byte/word counts and consistency as in STEP 7.
4. Build and download the configuration to the FCS.

Verification and Diagnostics

1. Physical layer: Verify the link LED on each DP/DP Link port is solid green (cyclic exchange). Verify LEDs on the S7-414-4H X1 port and on the Yokogawa ALP121 module.
2. STEP 7 online diagnostics: In HW Config, right-click the DP/DP Link slave and choose DP Slave Diagnostics. Confirm the slave is in Data Exchange state and the slot configuration matches the engineering.
3. Buffer the SFC14 return value: Capture MW100/MW102 into a status DB and trend in WinCC or HMI to confirm 0000 (no error) under steady state and 0000 immediately after Yokogawa FCS restart (re-establishment within one DP cycle).
4. Yokogawa side: View the PROFIBUS diagnostic in CENTUM Builder; verify the DP/DP Link is in Data Exchange and all configured slots show OK.
5. Loopback test: Send a fixed pattern from S7-414-4H to Yokogawa, mirror it back via Yokogawa logic, and read it back on S7. Compare pattern to received value in OB35 to validate full bidirectional integrity.

Troubleshooting Matrix

Safety and Commissioning Notes

• The S7-414-4H is a redundant CPU. Both CPUs participate on the same DP segment; the active CPU holds the token. Verify in HW Config that the redundant partner does not also try to claim the bus as a separate master - by default the H system handles this automatically, but a re-check after a CPU swap is recommended.
• Functional safety data must not be routed through a non-safety-certified link unless the integrated PROFIBUS safety (PROFIsafe) layer is used end-to-end. The DP/DP Link itself is not PROFIsafe-compatible; do not pass safety signals through it.
• Apply shield bonding at both cable ends with low-impedance connections. The recommended shield current capacity is below 1 kA for typical plant environments; check against site fault levels.
• Document the byte map of both segments in the project documentation. The map must show: tag name, byte offset, scaling, engineering units, and direction (read/write from S7 perspective).
• When replacing a DP/DP Link in operation, set both masters to STOP, swap the device, re-apply power, and restart masters in sequence. Hot-swap is not supported by the link.

Frequently Asked Questions