Siemens SINUMERIK 840C - Manual (Page 865)

12 Functional Descriptions 07.97
12.11.2 ENDAT absolute encoder (SW 5.2 and higher)
12.11.2.6 Behaviour on power on)
If NC MD 1808* bit 0 is set the NC MD 1808* bit 3 ”Absolute offset valid” is checked for the
corresponding axes. If both bits are set, the axis-specific interface signal ”Reference point
reached” is already set on power-on.
12.11.2.7 Special case ” Parking axis ”
With the axis-specific interface signal ”Parking axis”, the interface signal ”Reference point
reached” is reset on an axis with an absolute encoder too.
If the axis-specific interface signal ”Parking axis” is cancelled and
• NC MD 1808*, bit 3, absolute offset valid, is not set, referencing is suppressed
• NC MD 1808*, bit 3, absolute offset valid, is set, referencing is performed immediately and
the interface signal ”Measuring system referenced = Referenced point reached” is set.
12.11.2.8 Absolute encoder error
With the absolute encoder function, errors can occur both in and outside the encoder.
Therefore, if an error occurs it is first necessary to check the transmission line between the
encoder and the absolute module.
All absolute encoder errors are displayed axis-specifically in the control with the error message
”Absolute encoder defective”.
The precise type of error can be found in the line ”Service number” in the menu service
status display. The error number is displayed.
If the error numbers are converted to 8-bit binary numbers (calculator accessory), the single
error sources are defined as follows:
Bit 0 Not defined
Bit 1 Not defined
Bit 2 Alarm from ENDAT protocol
Bit 3 CRC error
Bit 4 TIMEOUT (shows missing start bit after 4.5 ms)
Bit 5 Wrong (old) hardware
Bit 6 Not defined
Bit 7 Drive ascertains ENDAT encoder error
Detailed information about the causes of error detected by the drive is provided in drive MD
1023* measuring system motor absolute track or in drive MD 1033*, direct measuring system
absolute track.
Remedy:
• Check absolute encoder for damage
• Check for correct fit of connectors between absolute encoder and servo loop
• Replace encoder and motor.
12.11.3 Range extension with ENDAT absolute encoder (as from SW 6)
12.11.3.1 Description of function
If an ENDAT encoder is used as the indirect measuring system, a range extension can be set
in NC MD 1808*, bit 7. Encoder overflows are recorded and stored in the NC-CPU (SRAM) as
a rough encoder position.
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SINUMERIK 840C (IA)