Resolving SIMOREG 6RA70 A083 Alarm on S7-400 PROFIBUS

Problem Overview: SIMOREG 6RA70 A083 with CPU 412-2DP on PROFIBUS

When integrating a Siemens SIMOREG 6RA70 DC Master drive fitted with a CBP2 communications board as a PROFIBUS-DP slave on a SIMATIC S7-400 CPU 412-2DP master, the most common first-time fault is the drive raising alarm A083 immediately after bus commissioning, even though STEP 7 reports the slave as healthy in the diagnostic buffer and the CBP2 LED indicates green cyclic exchange. The drive refuses every subsequent setpoint write, and the operator panel displays A083 instead of an active ready-to-run state.

On SIMOREG 6RA70 firmware (typical SW 2.1 and later, including SW 3.x), A083 is defined as: "Field-bus setpoint channel not released — Control word 1, bit 10 = 0." The drive firmware intentionally ignores all process data words (PZD) until bit 10 of STW1 (the first PZD output word) is asserted by the master. The fault is therefore a master-side commissioning gap, not a hardware defect.

This article explains how to release the setpoint channel, choose the correct PPO type, and select the right SFC or SFB for cyclic and acyclic communication between an S7-400 CPU 412-2DP and a 6RA70 + CBP2.

Root Cause of A083 — Four Contributing Factors

1. STW1 bit 10 not set in PZD1 output. The first word of the cyclic output to the drive must carry a value with bit 10 = 1 (minimum 0x0400). Until that bit is asserted, the drive parks every PZD and reports A083.
2. PPO type mismatch between master and slave. The number of PKW and PZD words selected in HW Config must equal the PPO type selected on the drive (parameter U734). A mismatch causes A080/A081 (configuration error) or a silent drop to PPO 3.
3. Direct peripheral I/O access on a consistent multi-word telegram. PPO types with more than 4 bytes or 3 bytes of PZD require SFC14 (DPRD_DAT) for reads and SFC15 (DPWR_DAT) for writes. Using PIW/PQW directly on a consistent slot produces inconsistent values and triggers A083 indirectly.
4. CBP2 still initialising when PZD writes start. The CBP2 module has its own internal startup; if the master starts transmitting PZD before the CBP2 reports "Data Exchange", the first frames are dropped and A083 may persist until a clean cycle occurs.

Hardware and Software Prerequisites

PPO Type Selection Reference

The PROFIdrive PPO (Parameter/Process Data Object) type defines the structure of the cyclic telegram exchanged between the DP master and the 6RA70 + CBP2. The 6RA70 supports PPO types 1 through 5:

For the typical commissioning scenario where the goal is to release the setpoint channel and clear A083, PPO 3 is the recommended configuration: two PZD out (STW1 + main setpoint), two PZD in (ZSW1 + actual speed), no PKW channel. PPO 3 produces a 4-byte telegram, which fits the S7-400 non-consistent direct access boundary, so no SFC14/SFC15 are required.

SFC / SFB Selection Matrix

The selection rule is mechanical: if the PZD fits in ≤ 4 bytes non-consistent, use PIW/PQW directly. If it exceeds 4 bytes or is consistent, SFC14/SFC15 is mandatory. Acyclic parameter access on the 6RA70 + CBP2 is typically done via DPV1 records (SFB52/SFB53) when the CBP2 is configured for DPV1; otherwise the S7-style SFC58/SFC59 is used.

Step-by-Step Resolution

Step 1 — Verify physical and bus-level PROFIBUS

Confirm the CBP2 slave LED shows a steady green "Data Exchange" state. In STEP 7, open the CPU → Module Information → Diagnostic Buffer and confirm there are no station failure (SF) entries for the slave address. Resolve any bus errors before continuing.

Step 2 — Configure PPO type in HW Config

1. Open HW Config (STEP 7 V5) and locate the DP slave representing the 6RA70 + CBP2.
2. Open the slave properties and select PPO type 3 (or 4 if more PZD are needed).
3. Note the assigned I/O addresses. For PPO 3 the default slot 0 base is typically 256 (hex 0x100), giving PIW256..PIW259 / PQW256..PQW259.
4. Compile and download the hardware configuration to the CPU 412-2DP.

Step 3 — Match the PPO type on the drive

On the 6RA70 side, set the CBP2 PPO type to match the master configuration:

Step 4 — Force the setpoint channel release (clears A083)

The single action that removes A083 is to write a value with bit 10 = 1 in the first PZD output word (STW1). For PPO 3 this is PQW 256 (low word of the first double word at base 256). In ladder logic (OB1):

// Release setpoint channel and command ON
      L  W#16#047F        // bit 10 = 1 plus ON pattern
                          // 0x0400 = STW1.bit10 set
                          // 0x007F = bits 0-6 set (ON/OFF1, OFF2, OFF3,
                          //          enable, ramp enable, setpoint enable)
      T  PQW 256           // PZD1 output, word 0 — clears A083

The minimum value that clears A083 is 0x0400 (only bit 10 set). The typical operational pattern while running is 0x047F. The bit must remain set throughout operation; if the application ever clears PQW256 to zero (for example during an OB100 startup with no initial value), A083 reappears immediately.

Step 5 — Use SFC14/SFC15 when the PPO requires consistent transfer

For PPO 4 (12 bytes PZD), PPO 5 (20 bytes PZD), or any consistent multi-word telegram, call SFC14 and SFC15 from a cyclic OB. Place the PZD data in a shared DB to allow other logic blocks to access the words symbolically:

// In OB1 — read inputs from slave
CALL SFC 14
       LADDR   := W#16#100        // base address 256 decimal
       RET_VAL := MW 100          // 0 = OK, see error table
       RECORD  := P#DB100.DBX0.0 BYTE 12  // 12 bytes for PPO 4 input PZD

// In OB1 — write outputs to slave
CALL SFC 15
       LADDR   := W#16#100
       RECORD  := P#DB100.DBX12.0 BYTE 12 // 12 bytes for PPO 4 output PZD
       RET_VAL := MW 102

DB100 layout for PPO 4: bytes 0..11 = input PZD (ZSW1, actual speed, current, torque, blank, blank), bytes 12..23 = output PZD (STW1, main setpoint, aux setpoints). Set bit 10 of the first word (byte 12, bits 8..15) to 1 to release the setpoint channel and clear A083.

Step 6 — Verify SFC14/15 return codes

Control Word 1 Bit Map (STW1 — PZD1 word 0)

Status Word 1 Bit Map (ZSW1 — PZD1 word 0 input)

Bit 9 of ZSW1 is the master's echo that the drive has accepted STW1 bit 10. When ZSW1 bit 9 reads back as 1, the setpoint channel is released and A083 is cleared.

CBP2 Diagnostic Parameters

Verification Checklist

1. The 6RA70 OP1S / DriveMonitor shows alarm A083 inactive.
2. Status word bit 9 (ZSW1 bit 9) reads back as 1.
3. Writing PQW 256 = 0x0400 alone clears A083 within one DP cycle (≤ 10 ms at 1.5 Mbit/s).
4. A ramp from 0 % to 50 % setpoint is followed by the motor without F030 (overspeed), F035 (field current missing), or F042 (tachometer fault).
5. Diagnostic buffer on the CPU contains no station failure entries related to the slave address.
6. SFC14/SFC15 return RET_VAL = 0 on each cycle (when used).
7. Parameter r047.001 on CBP2 reads 4 (Data Exchange) and remains stable.

Extended Troubleshooting Matrix

Commissioning Procedure Summary

1. Set PROFIBUS address on CBP2 (DIP switch or P918) and on the CPU 412-2DP master (HW Config).
2. Enable terminating resistors at both ends of the PROFIBUS segment.
3. Import the CBP2 GSD file (SIEM80D9.GSD) into STEP 7 and configure the slave at the desired address.
4. Select PPO type in HW Config and match U734.001 on the drive.
5. Download the hardware configuration to the CPU 412-2DP.
6. Place SFC14/SFC15 calls in OB1 if the PPO type requires consistent transfer.
7. In OB100, initialise PQW 256 = 0x047F so that the first cycle after restart already releases the setpoint channel.
8. Power the drive, clear any faults via OP1S, then write 0x047F to PQW 256.
9. Verify ZSW1 bit 9 = 1 and confirm that A083 has cleared.
10. Run a low-speed ramp (5 %) and verify torque and current feedback.
11. Save the project, back up the drive parameter set via DriveMonitor, and document the PPO type and addresses for maintenance.

Safety Considerations

Migration Notes for TIA Portal and S7-1200/1500 Masters

If the same 6RA70 + CBP2 is later migrated from an S7-400 CPU 412-2DP master to an S7-1200 or S7-1500 master, the connection procedure is described in the official TIA Portal communication manual at Configuring logical network connections between two PROFIBUS devices. Key differences from the S7-400 implementation:

• On S7-1200/1500, all PROFIBUS slave I/O is consistent, so the PUT/GET pattern or the DPV1 record blocks (RDREC / WRREC) replace SFC14/SFC15.
• The CBP2 must be configured for DPV1 mode (U734.004 = 1) to use the DPV1 record interface.
• The STW1 bit 10 requirement for clearing A083 is unchanged because it is enforced by the drive firmware, not the master.
• The hardware configuration migrates via TIA Portal "Migrate project" from STEP 7 V5; the GSD file (SIEM80D9.GSD) re-imports automatically.

Differences Between A083 and F083

A083 is the software-side setpoint release fault; F083 is a hardware-side bus fault. The same fix (STW1 bit 10 = 1) clears A083 only. F083 requires physical intervention on the CBP2 or bus segment.

FAQ