ifm electronic RN3001 - Manual (Page 12)

Encoder with Profibus interface
12
9.3.2 Preset function
The preset function enables adaptation of the encoder zero point to the
mechanical zero point of the system�
► Set the encoder actual value to the requested preset value�
> The requested zero point drift is calculated by the device and stored in an
EEPROM (non-volatile) which takes less than 40 ms�
The preset value is activated in the peripheral output double word by setting bit
31 (adopted with rising edge)� Setting is made automatically after transfer of the
scaling parameters, i�e� the preset value refers to the scaled actual value�
Data bits
Bit 4 31 30 29...0
Master → encoder 1 0 Transfer of the requested value
(= preset value)
Encoder → master 0 0 New = requested process actual value is transferred
Master → encoder 0 0 Reset bit 31 - normal mode
Encoder → master 0 0 New = requested process actual value is transferred
Only set the preset while the encoder shaft is at standstill� If the shaft moves
during this time, shifts are possible since runtimes occur via the bus when the
preset value is set�
Note on the singleturn version
The process can be transferred to the singleturn version – here bit 15 is used to
activate the preset value� With high-resolution singleturn encoders (16 bits) no
preset values > 32767 (15 bits) can be set in Class 2 (MSB is used to activate the
preset value)� If this function is requested, one of the manufacturer-specific ifm
classes has to be selected (transfer here also in 32-bit format for the singleturn)�