Resolving Simovert Masterdrive 008 On Lockout via PROFIBUS

Resolving Simovert Masterdrive 008 (On Lockout) When Starting via PROFIBUS

The Siemens Simovert Masterdrive (6SE70 / 6SE71 series) controlled through PROFIBUS DP from an Allen-Bradley CompactLogix controller frequently shows alarm 008 (On Lockout / Switch-On Inhibit) on the PMU operator panel during commissioning. This fault means the drive has received an OFF2 or OFF3 condition, or the controller has not signaled that it is the active command source. The drive refuses to close its gating and run the motor until every inhibit is cleared and the proper control-word pattern is written cyclically from the PLC.

This reference walks through the parameterization, control-word bit pattern, CompactLogix I/O assembly mapping, and verification sequence needed to clear 008 and start the drive cleanly over PROFIBUS. It applies to Simovert Masterdrive Motion Control (VC) and Vector Control (VC-MC) units using CBP / CBP2 PROFIBUS option boards.

1. Background: Control Word, Status Word, and PROFIdrive Profile

The Simovert Masterdrive implements the PROFIdrive profile (Version 2 / V3 PN-compatible mapping on Classic PROFIBUS). Two 16-bit process-data words are exchanged cyclically between the DP master (CompactLogix via SST PROFIBUS scanner, or third-party gateway) and the drive:

• Control word 1 (STW1) — written from PLC to drive. Source connector: parameter P554.1. Connector index 3001 = STW1 bit-by-bit (one per bit).
• Status word 1 (ZSW1) — read from drive to PLC. Sink connector: parameter P734.1. Connector index 32 = status word 1 (r552-derived actual state word).

1.1 Control Word 1 Bit Assignment (PROFIdrive)

The drive issues 008 On Lockout whenever STW1 bit 10 (Control by PLC) = 0, OR when any of bits 1 (OFF2) and 2 (OFF3) = 0, OR when P555-P560 inhibit sources are asserted. The drive will not close the gating until every condition in this matrix is satisfied.

1.2 Status Word 1 Bit Assignment (PROFIdrive, read as ZSW1 = 32)

2. Root Cause Analysis of Fault 008 (On Lockout)

On a Simovert Masterdrive, alarm 008 is the visible PMU-side mirror of bit 6 (Switch-On Inhibit) in status word 1. It is a logical condition, not a latched fault in the fault buffer. The PMU shows 008 any time the drive has been parameterized for bus control but the STW1 received from the master is not the exact pattern required by the drive's state machine.

The five most frequent root causes are:

1. STW1 bit 10 (Control by PLC) = 0. The drive assumes local / terminal command and refuses to honor STW1 bits 0-7. This is the single most common cause when the PLC writes the wrong word or the bus scan is in STOP.
2. STW1 bit 1 (OFF2) = 0. Wired as a hardwired safe stop (typically P555 = a digital input). If that input is open or the parameter is set to 0, OFF2 is permanently active.
3. STW1 bit 2 (OFF3) = 0. Same principle as OFF2 but for quick stop. Often wired to a thermistor or external safety relay.
4. P555-P560 not initialized to "inactive". By default, these parameters are 0, which the firmware interprets as a permanent OFF2/OFF3. Each must be set to a connector index that yields logic 1 (e.g. a permanently-high fixed connector such as B0000 or a real DI mapped to 1).
5. Cyclic I/O not running. If the DP slave has dropped out (diagnosis active on the scanner, watchdog expired, baud-rate mismatch), the drive holds the last good STW1 or reverts to "0". Check the CBP LED state and the scanner diagnostic buffer.

3. Prerequisites

• Simovert Masterdrive with CBP or CBP2 PROFIBUS option board installed and terminated.
• Allen-Bradley CompactLogix processor with a PROFIBUS DP master module (1784-PKTx, SST-PFB-SLC, ProSoft, or HMS Anybus X-gateway with CompactLogix EtherNet/IP upstream).
• Siemens GSD file SIEM808F.GSD (for CBP) or the matching CBP2 GSD imported into the scanner configuration tool.
• DriveMonitor or Simovert commissioning software for parameter download (or PMU keypad for manual entry).
• Reference documentation: Siemens Industry Online Support — search for "Simovert Masterdrive Compendium" for parameter list and 6SE70 Operating Instructions.

4. Step-by-Step Parameter Configuration

The following sequence clears 008 and establishes PROFIBUS control. All parameter changes must be saved with P971 = 1 (save to EEPROM) or the drive reverts after a power cycle.

1. Restore factory defaults (optional, recommended on first commissioning):
   P970 = 1 starts a factory reset. Wait for drive to reboot.
2. Set command source to STW1 from PROFIBUS:
   P554.1 = 3001 (control word 1, bit-by-bit)
   Alternative: P554.1 = 3100 routes the entire word at once. 3100 is convenient when no bit-by-bit override is needed.
3. Set status sink to ZSW1 (word 32):
   P734.1 = 32 (status word 1). Connector 33 is the actual value word; use 32 for the boolean status word.
4. Clear the OFF2 / OFF3 / Enable-OFF chain (P555 - P560):
   These parameters select the source for each control bit. They default to 0, which the firmware treats as "permanently false" (= OFF2 / OFF3 active).
   P555 = 0 OFF2 source (set to a fixed-high connector if no hardware)
   P556 = 0 OFF3 source
   P557 = 0 Enable operation
   P558 = 0 Enable ramp generator
   P559 = 0 Unfreeze ramp generator
   P560 = 0 Setpoint enable
   
   Setting each to 0 is the "logic 1" no-inhibit state in the default parameterization. If your installation requires a hardware safe-stop on OFF2, leave P555 wired to a digital input and map that input to connector 1 (or 2, 3, etc.) instead of leaving it at 0.
5. Map the speed setpoint:
   P443 = 3002 (main setpoint = HSW, the 16-bit normalized speed reference from the PLC). Connector 3002 receives the 16-bit normalized value; connector K3002 is the smooth-filtered version.
6. Wire the pulse enable / setpoint enable:
   P561 = 3103 (pulse enable from bit 3 of the second control word)
   P564 = 3106 (setpoint enable from bit 6 of the second control word)
   These are recommended by Siemens for separation between gating enable and setpoint release.
7. Save parameters:
   P971 = 1 → wait → P972 = 1 to reboot the drive and load the new parameter set.
8. Verify cyclic communication:
   Read r550 (Control Word 1) and r552 (Status Word 1) on the PMU. r550 must equal the word the PLC is transmitting. r552 must show bit 6 = 0 (no Switch-On Inhibit).

5. CompactLogix Side: Building the Control Word

When using a third-party PROFIBUS master gateway to CompactLogix, the drive is mapped as a DP-V0 slave with two words of process data (4 PKW + 2 PZD is also possible, but the typical 6SE70 mapping is 2 PZD in / 2 PZD out for cyclic, plus 4 PKW for parameter channel).

5.1 Output Assembly (PLC → Drive)

The minimum pattern to exit 008 and run forward is:

That pattern = bits {0,1,2,3,4,5,6,10} set → 0x047F (hex). All other bits 0.

5.2 Ladder Snippet for Control Word

(Sample RSLogix 5000 / Studio 5000 structure)
Local:5:I.Data[0]  // STW1 IN (drive → PLC)  Status word 1
Local:5:O.Data[0]  // STW1 OUT (PLC → drive) Control word 1
Local:5:O.Data[1]  // HSW OUT speed setpoint

// Build STW1 bit-by-bit
XIO(FaultResetRequest) AND ONS(AckEdge) -> STW1_bit7
XIC(RunRequest)        -> STW1_bit0
XIC(AlwaysOn)          -> STW1_bit1   // OFF2 inactive
XIC(AlwaysOn)          -> STW1_bit2   // OFF3 inactive
XIC(AlwaysOn)          -> STW1_bit3   // Enable operation
XIC(AlwaysOn)          -> STW1_bit4
XIC(AlwaysOn)          -> STW1_bit5
XIC(AlwaysOn)          -> STW1_bit6
XIC(PLC_Active)        -> STW1_bit10  // Control by PLC

5.3 Sequencer State for Edge-Triggered ON/OFF1

The PROFIdrive state machine requires bit 0 to be a rising edge. If you hold bit 0 = 1 continuously, the drive re-arms only when it sees 0→1 again after a stop. Implement a one-shot:

// Rising edge generator on RunRequest
XIC(RunRequest) XIO(PrevRun) ONS(RunEdge) -> RunLatch  
XIO(RunRequest)                         -> RunLatch (reset)
XIC(RunLatch) -> STW1_bit0

6. GSD File Configuration on the PROFIBUS Master

Whether the DP master is a Siemens S7 / TIA Portal master, a Rockwell 1784-PKTX, or a generic third-party scanner, the same GSD principles apply. The Siemens documentation Configuring GSD drives for PROFIBUS DP describes the canonical insertion pattern when a Simovert Masterdrive appears as a GSD device on a DP master system. The relevant points:

• Insert the CBP / CBP2 device from the device catalog using the GSD identifier 808F hex (Siemens CBP family).
• Select the cyclic I/O module "PPO Type 1" (4 PKW + 2 PZD) or "Standard Telegram 1" (2 PZD) as required.
• Set the PROFIBUS address on the CBP DIP switch to a free address and verify that it matches the master configuration.
• Configure consistent bus parameters (baud rate 1.5 / 3 / 6 / 12 Mbps) and watchdog time so that the scanner does not time out on brief gaps.

7. Verification Procedure

1. Power the drive, wait for 009 (Ready) on the PMU.
2. Confirm cyclic communication: CBP LEDs steady green (or green + flashing yellow for token-passing); check r550 matches the PLC's transmitted STW1 word.
3. Set STW1 = 0x047F (no run command). Verify ZSW1 (r552) bit 0 = 1 (Ready), bit 1 = 1 (Ready to Operate), bit 6 = 0 (no Switch-On Inhibit). The 008 alarm clears.
4. Pulse bit 0 from 0 to 1. ZSW1 bit 2 transitions to 1 (Operation Enabled). Motor fluxes and ramps to the HSW setpoint.
5. Toggle bit 0 to 0. Drive ramps down along the active decel ramp (P464), ZSW1 bit 2 falls to 0.
6. Verify "Run bit" (status word 1 bit 2 = Operation Enabled) is now TRUE in the PLC status word. This is the bit that reads 1 while the drive is running; bit 1 is "Ready to Operate", which is on even when not running.

8. Troubleshooting Matrix

9. Edge Cases and Field-Proven Caveats

• Bit 0 must be a rising edge, not a level. Continuous bit 0 = 1 from power-up may not start the drive after a fault-clear; the drive only re-arms on a 0→1 transition.
• P734.1 = 33 vs 32. Connector 33 is the status actual value word (numerical state for display); 32 is the boolean status word used by the state machine. The Run bit is in connector 32, bit 2.
• PMC and VC variants differ in P554 handling. On 6SE70 VC (Vector Control) firmware, the recommended P443 is 3002 with smoothed connector K3002; on VC-MC the setpoint path can be different. Always check against the parameter list for the exact order number.
• Watchdog behavior. If the DP master scan drops for longer than the CBP watchdog (default 1000 ms), the drive coasts and shows 008 again until cyclic communication resumes and the proper STW1 is received.
• PMU control vs PLC control mode toggle. When P554.1 is changed back to 2100 (PMU local) the drive becomes locally controllable, but the PLC cannot write STW1. Going back to 3100 or 3001 returns bus control. The transition itself is a normal "switch-on inhibit" event and clears the next time STW1 bit 10 = 1.

10. CompactLogix-Specific I/O Mapping Reference

When the CompactLogix is talking to the drive through a PROFIBUS-DP gateway (e.g. ProSoft PTQ-PDPMV1 or SST-PFB-CLX), the gateway exposes the cyclic PZD as integers in the input / output assemblies. Typical mapping:

11. Recommended Final Parameter Set

This is the conservative, proven pattern that combines the suggestions from the troubleshooting thread with Siemens recommended practice:

P443  = 3002    ; Main setpoint from HSW (normalized)
P554.1= 3100    ; Command source = Control word 1 (full word)
P555  = 0       ; OFF2 source = logic 1 (no hardware, or wire to fixed-high)
P556  = 0       ; OFF3 source = logic 1
P557  = 0       ; Enable operation
P558  = 0       ; Enable ramp generator
P559  = 0       ; Unfreeze ramp generator
P560  = 0       ; Setpoint enable
P561  = 3103    ; Pulse enable from STW2 bit 3 (alternative path)
P564  = 3106    ; Setpoint enable from STW2 bit 6
P734.1= 32      ; Status word 1 sink
P971  = 1       ; Save parameters
P972  = 1       ; Reboot drive