301711

Access Diagnostics > Parameters > Motor Data (MD) for the affected axis/drive. Navigate to MD 1028 and note the current SSI transmission length value.

Calculate required transmission bits: (MD 1021 multiturn bits) + (MD 1022 singleturn bits) + (MD 1027 status bits). Document this total.

Ensure MD 1022 is the actual resolution in bits, not the decimal resolution value.

If MD 1028 is less than the calculated total, increase MD 1028 to match or exceed the required bit count. Consult the SSI encoder datasheet for maximum supported transmission length.

Do not arbitrarily increase MD 1028 beyond the encoder's hardware capability; this will cause transmission errors.

Save parameters (MD), perform a SINUMERIK cold restart (Power ON/OFF cycle), and verify alarm 301711 clears during NCK initialization.

Review the motor measuring system encoder datasheet and verify the actual bit widths supported. Cross-reference with the axis configuration in the HMI or via SCOUT (Siemens Configuration Utility).

Check if MD 1021 and MD 1022 were recently modified. Use the parameter change history or backup files to compare old vs. new values.

A common mistake is confusing bit count with decimal resolution (e.g., 4096 resolution ≠ 12 bits).

Reduce MD 1021 and/or MD 1022 to match the encoder's actual specifications, or verify that MD 1028 is large enough to accommodate the new bit widths.

Reducing multiturn bits will limit absolute position range; ensure this does not conflict with machine travel limits (MD 32000–32002).

Save parameters, perform NCK restart, and confirm alarm 301711 is resolved.

Navigate to MD 1027 and verify the status/parity bit count. Compare with the encoder manual to ensure this reflects actual hardware capabilities.

If MD 1027 was recently increased, consider whether additional status bits are truly necessary. If not, restore it to the encoder manufacturer's recommended value.

Reducing status bits may disable encoder error detection; consult your safety/quality team before making this change.

Alternatively, increase MD 1028 (SSI transmission length) to accommodate the higher MD 1027 value, provided the physical SSI interface supports the longer cycle time.

Increasing transmission length may increase encoder cycle time and impact axis response; verify servo loop stability after adjustment.

Save parameters, restart the NCK, and monitor for alarm 301711 and any related servo instability.