Code 201940: <location>IF1: PB/PN clock cycle synchronism not reached
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical <location>IF1: PB/PN clock cycle synchronism not reached alarm. Immediate attention from a qualified operator or maintenance technician is required to prevent secondary damage to the equipment or spoiled parts during the manufacturing cycle. Always ensure standard safety and LOTO procedures are followed before accessing electrical cabinets.
Official Troubleshooting Steps
Message value: Drive object: All objects Reaction: NONE Acknowledge: NONE Cause: The bus is in the data exchange state and clock synchronous operation has been selected using the parameterizing telegram. It was not possible to synchr onize to the clock cycle specified by the master. - the master does not send a clock synchronous global control telegram although clock synchronous operation was selected when configuring the bus. - the master is using another clock synchronous DP clock cycle than was transf erred to the slave in the parameterizing telegram. - at least one drive object (that is not contro lled from PROFIBUS/PROFINET) has a pulse enable. Remedy: - check the master application and bus configuration. - check the consistency between the clock cycle input when configuring the slave and clock cycle setting at the master. - ensure that the pulses of drive objects that are not controlled by PR OFIBUS/PROFINET are not enabled. Only enable the pulses after synchr onizing the PROFIBUS/PROFINET drives. Note: IF1: Interface 1 PB: PROFIBUS PN: PROFINET
Source: SINUMERIK 840D sl / 840Di sl / SINAMICS S120 Diagnostics Manual (DAsl, 03/2009)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Siemens SINUMERIK 840D CNC Alarms
Siemens controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code 201940 on the SINUMERIK 840D CNC identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Siemens's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 4014 Siemens SINUMERIK 840D CNC codes.
Have a better solution?
Help the industrial community by sharing your repair experience for code 201940.
Need a searchable reference for more Siemens SINUMERIK 840D CNC manuals?
We structure equipment manuals into searchable code, title, cause, solution, safety note, and source-reference data. Send a PDF and example searched codes when you need public pages, private search, or structured exports.
Space reserved for Google AdSense / Industrial Affiliate Links
Monetization target for 2026