Baumer GE-GB-GXxxx - Manual (Page 19)

Manual_ProfibusDPV2_BIDE_EN.docx 19/41 Baumer IVO GmbH & Co. KG
22.11.12 Villingen-Schwenningen, Germany
Bit PR: Preset
If bit PR is set, the preset operation will be enabled. Once the Preset Acknowledge bit of the
input data is set, bit PR should be reset.
Bit REL: Preset Relative
If this bit is set, the function Preset Relative will be enabled, e.g. the actual position is added
the preset value as offset (negative values as complement on two). If this bit is not set, the
preset operation will be absolute. In other words, the encoder position is set to the preset
value.
6.4. Position readout
Position data are transmitted by telegram81 of the PROFIdrive profile as described above. Control access to
the data should only be enabled during clock-synchronous alarm. Only then it is guaranteed that the encoder
position is derived from the desired clock-synchronous bus cycle.
By principle, there could also be a direct control access to the parameterized I/O address using the peripheral
input words. We strongly recommend to refrain from this in clock-synchronous operation, since in this case
consistency and clock synchrony are not ensured.
6.5. Error signals in G1_XIST2
Bit 15 in G1_ZSW1 means that the value in G1_XIST2 is not a position value but an error code. Should
several errors occur at the same time only the first one will be transmitted.
Value Error Significance
0x0001 Position error Presently the encoder cannot provide a
correct position
0x0F01 Unknown command In G1_STW1 the master has transmitted a
command which is unknown to the encoder
0x0F02 Sign-of-Life error (Master) Number of admissible failures in the master-
sign-of-life has been exceeded
0x0F04 Synchronisation error Number of admissible failures in the bus
cycle signal has been exceeded
6.6. Preset function
Preset default setting is 0. Preset alteration is enabled by acyclic parameter 65000. The value is saved
volatile, i.e. it is lost at encoder power off. For non-volatile saving utilize parameter 971.
The actual preset operation is triggered by output word „G1_STW1“ bit 12. A feedback after a successful
operation is given by input word „G1_ZSW1“, bit12. This bit remains until the control will reset the
corresponding bit in the output word.
The preset value (volatile) must not be confused with the internal preset offset (non-volatile). The preset-
offset is automatically saved in the non-volatile memory so that the encoder will be in the same position after
power off and at power on.
The preset effect on position value G1_XIST1 can be compensated by parameterization („G1_XIST1 affected
by Preset“). In this case G1_XIST1 and G1_XIST2 provide different position values. G1_XIST2 is always
affected by preset.
Upon performing a preset operation an internal offset value is calculated and immediately saved non-volatile
in EEPROM. EEPROM provides 1 million writing cycles, however, frequent software or event-triggered preset
operations can exhaust the service life despite this high number of writing cycles. This should be considered
in the control software layout.