Resolving MICROMASTER 4 F0070 Fault: PROFIBUS Control Word Setup

1. Problem Overview: F0070 on a MICROMASTER 4 with PROFIBUS DP

A MICROMASTER 420 / 430 / 440 (MM4) drive configured as a PROFIBUS-DP slave stops responding to the PLC. The PLC is sending a control word of 0x1151 (word 1) and a frequency setpoint of 0x4000 (word 2) in the PZD output area, the bus is reported as OK, the parameter set has been validated (P0927), yet the drive trips on F0070 ("No setpoint via telegram") and refuses to run the motor in either direction.

The original parameter set reported in the field is:

The bus cabling, GSD file selection, and the I/O address mapping of the PLC are functional — the drive is exchanging cyclic PZD data, but it rejects the telegram because the control word does not contain the bit pattern the MM4 expects from a PROFIdrive-class master.

2. F0070 Fault Code Reference

F0070 is one of the most common PROFIBUS faults on MM4 inverters. Its definition in the MM420 / MM430 / MM440 parameter list is identical:

The fault is latched. A rising edge on STW1 bit 7 (fault acknowledge) clears F0070, but if the underlying control word is still invalid the drive will trip again on the next PROFIBUS cycle.

3. Root Cause: Decoding the 0x1151 Control Word

The control word the user is transmitting to PZD word 1 is 0x1151. Bit-decoded against the PROFIdrive profile used by MM4 (profile 1, application class 1, "speed control"):

Five bits are out of spec: bit 3 (no pulse enable), bit 5 (RFG held at zero), bit 6 (setpoint not enabled), bit 8 (JOG right pulled in), bit 10 (PLC is not signalling control), and bit 12 (MOP up). The MM4 state machine cannot transition past state S2 "Ready" into S3 "Operation enabled", and it raises F0070 because, from its perspective, no valid control word is being received — only a partial word with JOG and MOP commands.

4. MM4 PROFIBUS PZD Telegram Structure

The MM4 PROFIBUS option module (order number 6SE6400-1PB00-0AA0) defaults to the standard telegram 1 with 4 PZD words (2 OUT / 2 IN). The default PPO type is PPO1 (4 PKW + 2 PZD). Selecting a different PPO type in HW Config does not change the bit semantics of the PZD words; it only adds or removes the parameter channel (PKW).

The data sequence STW, HSW, ZSW, HIW is the only sequence the MM4 accepts. Swapping the order of the setpoint and control word will be silently accepted by the bus, but the drive will not run and will likely raise F0070 or F0072. See the official SINAMICS G / MICROMASTER 4: Essentials for PROFIBUS manual for the canonical mapping.

5. Control Word (STW 1) Reference for MM4

The complete, ready-to-use control word table for the MM4 in PROFIdrive profile:

The minimum run word is 0x047F (forward) or 0x0C7F (reverse). Anything that does not have bit 10 = 1 is treated as "no PLC control" by the MM4 state machine and will not start the drive.

6. Status Word (ZSW 1) Reference for MM4

Once the drive is running correctly, the PLC should read ZSW1 and confirm the following pattern before driving the process forward:

A healthy running MM4 should report ZSW1 = 0x0F31 at setpoint speed. The PLC should mask on bits 0, 1, 2, 9, 10, 11 to confirm the drive has reached the run state.

7. Frequency Setpoint (HSW) Scaling

The main setpoint word HSW is normalized to a 16-bit signed integer:

• 0x4000 (16384 decimal) = +100 % of P2000 (reference frequency)
• 0xC000 (-16384 decimal) = -100 % of P2000 (reverse direction)
• 0x0000 = 0 Hz

P2000 is the reference frequency, typically the motor nameplate frequency (50 Hz or 60 Hz). P2000 should match the motor rated frequency; the setpoint 0x4000 in the original report will command exactly P2000 Hz on the output, regardless of the actual motor rating.

For a 50 Hz motor, sending HSW = 0x2000 commands 25 Hz. For a 60 Hz motor, sending HSW = 0x4000 commands 60 Hz. Always set P2000 explicitly so that the HSW scaling is unambiguous across the fleet.

8. Required Drive Parameters for PROFIBUS Control

Beyond the user's reported set, several additional parameters must be set to make PROFIBUS control functional on MM420 / MM440. The complete list:

After writing these values the parameter set must be saved with P0927 = 15 followed by P0009 = 0 (drive ready) and a power cycle, otherwise the drive will revert to the previous values on the next power-up and F0070 will return.

9. Step-by-Step: Building the Correct Run Word

1. Verify PROFIBUS communication by reading the bus state on the PLC (e.g., Siemens S7: SFC 13 / SFB 53 "DPNRM_DG" or use the diagnostic buffer in STEP 7). The MM4 must report DP-Slave OK and the LED on the PROFIBUS option module must be solid green.
2. Reset any active faults. Set STW1 to 0x0080 (fault acknowledge only) for one bus cycle, then drop back to 0x0000. Verify ZSW1 bit 3 (fault present) reads 0.
3. Stage the run enable. Set STW1 to 0x047E for at least one bus cycle. The drive transitions from S1 "Switching on inhibited" to S2 "Ready for switching on". ZSW1 should read 0x0E21 (bits 0, 1, 6, 9 set).
4. Set the operation-enabled bit. Transition STW1 to 0x047F (forward) or 0x0C7F (reverse). ZSW1 should now read 0x0F31 within the ramp time (P1120). The motor accelerates to the speed commanded by HSW.
5. Adjust the speed by writing HSW. For 50 Hz operation at half speed, write 0x2000. For full speed, write 0x4000. For full reverse, write 0xC000 together with STW1 = 0x0C7F.
6. To stop, write STW1 = 0x047E (OFF1 ramp stop). The drive ramps down via P1121. To coast, write 0x047D (bit 1 cleared → OFF2). To quick-stop, write 0x047B (bit 2 cleared → OFF3).

10. PLC Programming: S7 Sample Using SFC14 / SFC15

The Siemens function block FC14 documented in the official MICROMASTER 4 PROFIBUS example wraps the read and write system functions. The same job can be done with SFC 14 "DPRD_DAT" (read consistent PZD) and SFC 15 "DPWR_DAT" (write consistent PZD) on the configured I/O addresses. A complete STL segment in STEP 7 V5.5:

// Inputs / outputs in the PLC's process image
// PIB 256..263   : 2 PZD words received from MM4 (ZSW1, HIW)
// PQB 256..263   : 2 PZD words sent to MM4 (STW1, HSW)
// DB10.DBX0.0    : User command "Run forward"
// DB10.DBX0.1    : User command "Run reverse"
// DB10.DBX0.2    : User command "Fault acknowledge"
// DB10.DBD4      : User speed setpoint, REAL Hz

// --- Build the control word ---
L 0
T DB10.DBW 12       // STW1 placeholder

// Bit 0  ON/OFF1
A DB10.DBX 0.0
= DB10.DBX 12.0
A DB10.DBX 0.1
= DB10.DBX 12.0

// Bit 1  OFF2 (1 = no coast)
SET
= DB10.DBX 12.1

// Bit 2  OFF3 (1 = no quick stop)
SET
= DB10.DBX 12.2

// Bit 3  Enable operation
A DB10.DBX 0.0
O DB10.DBX 0.1
= DB10.DBX 12.3

// Bit 4  Enable ramp generator
A DB10.DBX 0.0
O DB10.DBX 0.1
= DB10.DBX 12.4

// Bit 5  Unfreeze ramp generator
A DB10.DBX 0.0
O DB10.DBX 0.1
= DB10.DBX 12.5

// Bit 6  Setpoint enable
A DB10.DBX 0.0
O DB10.DBX 0.1
= DB10.DBX 12.6

// Bit 10 Control by PLC (mandatory)
SET
= DB10.DBX 13.2     // DB10.DBW12 bit 10 = byte 13 bit 2

// Bit 11 Reverse
A DB10.DBX 0.1
= DB10.DBX 13.3

// Bit 7  Fault acknowledge (rising edge)
A DB10.DBX 0.2
FP DB10.DBX 14.0
= DB10.DBX 12.7

// --- Scale the speed setpoint to 0x4000 = P2000 ---
L DB10.DBD 4        // speed in Hz, REAL
L 1.638400e+4       // 0x4000
*R
L 5.0e+1            // P2000 (or use P2000 from parameter)
/R
RND
T DB10.DBW 14       // HSW

// --- Write 4 bytes to drive via SFC 15 ---
CALL SFC 15
  LADDR   := W#16#100     // configured I/O start address
  RECORD  := P#DB10.DBX 12.0 BYTE 4
  RET_VAL := MW 20

// --- Read 4 bytes from drive via SFC 14 ---
CALL SFC 14
  LADDR   := W#16#100
  RET_VAL := MW 22
  RECORD  := P#DB10.DBX 16.0 BYTE 4

For a TIA Portal equivalent using the DPRD_DAT / DPWR_DAT instruction blocks, the same address pair is used and the DB layout is unchanged. The fully developed Siemens Industry Online Support example for FC14 is downloadable under entry ID 8894584.

11. Verification and Commissioning Checklist

Run through this matrix in the order given. Every check must pass before the drive is handed over to production.

12. F0070 and Related PROFIBUS Fault Matrix

When an MM4 reports an F-code over PROFIBUS, the fault is also written into drive parameter r0947 and the corresponding STW1 / ZSW1 bit pattern in the cyclic PZD data:

F0070 is the only one in this group that is purely a PROFIBUS control issue. If the drive is in F0071 / F0072, P1000 must be revisited to remove the USS source bit.

13. Frequently Asked Questions