Reading and Writing Danfoss FC 300 over PROFIBUS DP on S7-300

Overview

The Danfoss VLT FC 300 series drive exposes a Profidrive-compliant PROFIBUS DP interface that exchanges process data (PZD) and parameter data (PKW) with a Siemens S7-300 CPU 315-2DP. The CPU 315-2DP integrates a PROFIBUS DP master port on the X2 (DP) interface, eliminating the need for a CP 342-5 communications processor. Cyclic PZD words are read with the standard PIW (Periphery Input Word) and written with PQW (Periphery Output Word) instructions, while parameter channel access (PKW) and acyclic services use SFC14 / SFC15 (DPRD_DAT / DPWR_DAT) for consistency on word counts above four words.

This guide covers the complete configuration path: GSD file import, hardware configuration in STEP 7 / TIA Portal, PPO type selection, byte and word mapping, direct load/transfer (L/T) program examples for sub-4-word I/O, SFC14/15 block calls for larger PPOs, Profidrive parameter addressing for FC 300, scaling of current/frequency/frequency reference, and the verification checks used to confirm a healthy bus.

Prerequisites

• Hardware: SIMATIC S7-300 CPU 315-2DP (6ES7315-2AFxx-0AB0 or later), Danfoss FC 300 with PROFIBUS DP option card (MCA 101, ordering code 130B1100), and a PROFIBUS DP cable terminated at both ends (220 Ω termination resistors, both ON at the two physical end nodes only).
• Configuration software: STEP 7 V5.5 + SP2 (or later) with HW Config, or TIA Portal V13 SP1 / V14 / V15.1. The Danfoss GSD file DANFOSS0F.GSD (or DAFC3000.GSD, revision varies with firmware) must be installed before the FC 300 appears in the catalog.
• FC 300 firmware: Verify with parameter 15-61 "Option SW Version" that MCA 101 firmware is current. The Profidrive profile is supported across all FC 300 firmware versions, but a recent GSD is required if PPO type 7 or 8 is used.
• FC 300 PROFIBUS address: Set parameter 8-30 "Protocol" to "FC" (or "PROFIdrive" on newer firmwares), parameter 8-31 "Address" to a unique DP slave address (1-126). Default 1 will collide with most master default address spaces — change it.
• DP baud rate: FC 300 auto-detects up to 12 Mbit/s. Set the S7 master to 1.5 Mbit/s or 12 Mbit/s for the cable length used; the cable budget is the same as for any PROFIBUS DP segment.

Installing the Danfoss GSD File

1. Download the latest DANFOSS0F.GSD from the Danfoss Drives product page for the FC 300 / VLT AutomationDrive FC 300.
2. In STEP 7 V5.5: HW Config → Options → Install GSD File. Browse to the unpacked GSD directory and select DANFOSS0F.GSD.
3. In TIA Portal: Options → Manage General Station Description Files (GSD), browse the directory, and tick the FC 300 DP-V0 / DP-V1 device.
4. Close and reopen HW Config / the device catalog. The FC 300 appears under PROFIBUS DP → Additional Field Devices → Drives → Danfoss.

Hardware Configuration in STEP 7

1. Open the S7 station in HW Config and confirm the CPU 315-2DP is inserted in slot 2. The DP master port is on the CPU itself, not on a CP.
2. Place a PROFIBUS subnet on the CPU's DP interface and add the FC 300 from the catalog to that subnet at the same PROFIBUS address entered in FC 300 parameter 8-31.
3. Open the FC 300 slot configuration. The catalog exposes the FC 300 as slot 0 (drive object). PPO types are configured by selecting the slot configuration that matches the data length required.
4. Choose the PPO type. The available PPOs (Profidrive Profile Drive Technology) for FC 300 are summarized below.

5. STEP 7 assigns a logical base address (for example I 256..I 271 and Q 256..Q 271 for PPO 5). Record these — they are the offsets used by PIW/PQW in the user program.
6. Save, compile, and download the hardware configuration to the CPU.

PPO Layout and PZD Word Map

The PPO is laid out contiguously in the slave's I/O image. The first PKW words (if any) are the parameter channel; the trailing PZD words carry process data. For FC 300, the standard PZD map inside the drive is fixed regardless of PPO type and is described below.

Parameters that select additional PZD content on FC 300:

• 8-10 "Control Word Profile" — must be set to 0 (FC profile) or 3 (Profidrive) to expose the standard map.
• 8-50/8-51 — selection of which drive parameter appears in PZD3 OUT / PZD3 IN (motor current, DC-link voltage, torque, etc.).
• 8-70/8-71 — selection of which drive parameter appears in PZD4 and beyond.

Reading and Writing the PZD with Direct PIW / PQW (≤ 4 Words)

For PPO 3 and PPO 4 (no PKW), the entire PZD image fits in ≤ 4 words. STEP 7 guarantees consistency on the I/O update only when the access width matches the configured slot width. A direct L PIW / T PQW cycle, called once per OB1 scan, is acceptable on the S7-300 because the DP update is word-aligned and the FC 300 PZD slots are configured as word-sized.

STL example for PPO 3 (base address 256):

// Network 1: read FC 300 PZD
L PIW 256          // PZD1 IN: Status word (ZSW1)
T MW 20
L PIW 258          // PZD2 IN: Actual frequency (NIST_A)
T MW 22
// Network 2: write FC 300 PZD
L MW 10            // Control word (STW1) from user program
T PQW 256          // PZD1 OUT
L MW 12            // Speed setpoint (NSOLL_A) from user program
T PQW 258          // PZD2 OUT

Replace MW 10/12/20/22 with any DB word (e.g. DB10.DBW0) for a structured I/O image. The base address is the I and Q start address shown in HW Config for the FC 300 slot.

Using SFC14 (DPRD_DAT) and SFC15 (DPWR_DAT) for ≥ 5 Words

When the PPO has more than four PZD words, Siemens SFC14 "DPRD_DAT" and SFC15 "DPWR_DAT" are the only consistent way to copy the entire slave image to/from a DB. The SFCs handle the byte/word orientation in the master image and present the data to the user as a contiguous 16-bit word array.

STL example for PPO 5 (12 words PZD, base address 256, DB100):

// Read 12 PZD words from FC 300 into DB100 (bytes 0..23)
CALL SFC 14
  LADDR  := W#16#100            // decimal 256
  RET_VAL:="DB_RetVal_Read"
  RECORD :=P#DB100.DBX0.0 BYTE 24

// Write 12 PZD words to FC 300 from DB110 (bytes 0..23)
CALL SFC 15
  LADDR  := W#16#100
  RET_VAL:="DB_RetVal_Write"
  RECORD :=P#DB110.DBX0.0 BYTE 24

DB100.DBW0 = PZD1 IN (status), DB100.DBW2 = PZD2 IN (actual), … DB100.DBW22 = PZD12 IN. DB110.DBW0 = control word, DB110.DBW2 = reference, etc.

Accessing the PKW Parameter Channel

When a PPO with PKW (PPO 1, 2, 5, 6, 7, 8) is configured, the first 4 words of the slave image are the parameter channel. The FC 300 parameter channel uses the standard Profidrive PNU request/response mechanism described below.

Common request IDs (AK):

• 1 = Read parameter (single word)
• 2 = Write parameter (single word, non-volatile = RAM only)
• 3 = Write parameter to RAM only
• 5 = Read parameter (double word, 32-bit)
• 6 = Write parameter (double word, RAM only)
• 7 = Read parameter (array element)
• 8 = Write parameter (array element)

FC 300 parameter numbering is one-based. The Profidrive mapping (parameter 8-50/8-51 "PCD Read/Write Configuration") uses the FC 300 index; do not apply the PNU page conversion used on some Siemens master drives.

Acyclic Parameter Access over DP-V1 (SFB52/53/81)

For DP-V1 slaves (any modern FC 300 with MCA 101), acyclic read/write is preferred for non-time-critical parameter changes. The S7-300 does not have a generic SFB for this on the integrated DP master; it uses the Siemens SIMATIC function blocks for acyclic PROFIBUS DP-V1 communication (SFB 52 RDREC / SFB 53 WRREC) on the CPU 315-2DP from firmware V3.x onwards, with slot 0 and index 47 for parameter access per PROFIdrive parameter channel.

// Read FC 300 parameter 1-00 (configuration mode) acyclically
CALL SFB 52 // RDREC
  REQ     := TRUE
  ID      := DW#16#100         // DP master ID
  INDEX   := 47                // Profidrive parameter channel index
  MLEN    := 32                // Max record length
  RECORD  := P#DB120.DBX0.0 BYTE 32
  BUSY    := "SFB52_Busy"
  VALID   := "SFB52_Valid"
  ERROR   := "SFB52_Error"
  STATUS  := "SFB52_Status"
  LEN     := "SFB52_Len"

Scaling the Process Data

FC 300 PZD scaling follows Profidrive conventions. Apply these formulas in the S7 program after copying PZD words to a DB.

STL example: scaling motor current from PZD3 IN to engineering units in Amps.

// PZD3 IN is in DB100.DBW4 (PPO 5 layout). Convert to REAL Amps.
// FC300 rated current is in parameter 1-24 (1-25 / 1-26 are alternate units)
L DB100.DBW 4
ITD                    // sign-extend to double integer
DTR                    // convert to REAL
L 1.0                  // or L "Rated_Current_A" REAL tag from DB
/R
T "Motor_A"            // result in Amps

For a raw hex value of W#16#009B at PZD3 IN, the Profidrive formula gives 0x9B = 155, divided by 0x4000 (16384) × rated current. A common 10 A drive thus returns 155 / 16384 × 10 = 0.0946 × 10 = 0.946 A. The snippet 0.01 × WORD_TO_INT is a quick first-order scaling; replace it with the rated-current-aware formula for accurate readings.

Control Word (STW1) Bit Map

The FC 300 Profidrive control word occupies PZD1 OUT. Sequence the bits as follows for a normal start/stop/profile control.

Standard start sequence (STW1): 0x047E → 0x047F. Acknowledge a fault with 0x0480 → 0x047F. A coast stop is 0x047C. A quick stop is 0x047A.

Status Word (ZSW1) Bit Map

Commissioning and Verification

1. Download the HW Config to the CPU 315-2DP and put the CPU in RUN. The DP master enters the OPERATE state once a slave responds to the parameterization telegram.
2. Read parameter 15-61 on the FC 300 to confirm MCA 101 firmware and Profidrive version. Read 15-60/15-62 for the FC 300 master SW / option SW versions.
3. Watch the S7 diagnostic buffer. Bus errors are recorded with cause codes: 0x001F (station failure) → slave not responding at the configured address; 0x0044 (parameterization fault) → GSD mismatch or wrong PPO; 0x004D (configuration fault) → slot configuration mismatch.
4. Use the STEP 7 PLC → Monitor/Modify on the configured I/O to confirm PZD toggling. With the drive in HAND ON, force PQW 256 to W#16#047E and read PIW 256; bit 0 of ZSW1 should be 1 (ready to switch on).
5. Force PQW 256 = W#16#047F and verify ZSW1 = W#16#0C37 (ready, enabled, switch-on inhibited cleared). The drive should now ramp the motor to the value written to PQW 258 (NSOLL_A).
6. Read PQW 256 / PIW 258 in real time to verify the feedback (NIST_A) tracks NSOLL_A. For NSOLL_A = 0x4000, the actual frequency should be 100 % of motor nominal speed.
7. For parameter channel validation, write a request to read parameter 1-00 (PKE = 0x1001, IND = 0) and verify the response is 0x1001 / value = 0.

Troubleshooting Matrix

Cross-Reference and Standards

The PROFIdrive application profile is published by PI (PROFIBUS & PROFINET International). The current profile (PROFIdrive V4.2) is order no. 3.172 from PI, and is the governing document for the STW1/ZSW1 bit map and the PPO type definitions used here. The Schneider Electric TeSys T LTMR PROFIBUS DP Communication Guide and the TeSys Tera PROFIBUS DP Guide document the same PKE/IND/PWE channel layout and the SFC14/15-equivalent acyclic services, useful when validating the slave side. Rockwell Automation publication 2711-UM005 covers the same PI (input) / PO (output) direction convention used in the FC 300 slave configuration.

FAQ