Siemens alarm 10203: [Channel 1: ] NC start without reference point (action=%2<ALNX>)

What it means

Cycle start was requested while at least one axis that must be referenced has not yet reached its reference point. The 808D blocks program start; depending on MD20700 $MC_REFP_NC_START_LOCK the channel can also auto-start channel-specific referencing instead of alarming.

Likely causes

• Axes not referenced after power-up
• Reference cam or encoder zero mark not found during referencing
• Referencing configuration changed