Siemens SIMATIC FM 452, Manual

Page: 87 / 210

Machine Data and Cam Data
8-19
FM 452 Electronic Cam Controller
C79000-G7076-C452-04
Address Name Type Initial Value Comment
59.0 CNT_DIR BOOL FALSE Count direction:
0 = normal
1 = inverted
With the machine data “count direction”, you match the direction of the position detection to the direction
of axis movement.
You must also take into account all the directions of rotation of the transmission elements (for example
coupling and gearing).
•
Normal = ascending count pulses (incremental encoder) or encoder values (absolute encoder)
correspond to ascending actual position values
•
Inverted = ascending count pulses (incremental encoder) or encoder values (absolute encoder)
correspond to descending actual position values.
A lead time in conjunction with an absolute encoder (SSI) and inverted count direction is not
permitted.
Address Name Type Initial Value Comment
63.0
63.1
63.2 MON_WIRE
MON_FRAME
MON_PULSE BOOL
BOOL
BOOL TRUE
TRUE
TRUE
Monitoring:
1 = wire break
1 = frame error (must always be 1)
1 = missing pulses
Wire break
When monitoring is activated, the FM 452 monitors the signals
A, A, B, B, N and N of an incremental encoder. The monitoring detects:
•
Wire break
•
Short circuit on individual lines.
With incremental encoders without a zero marker, you must either
– deactivate the wire break monitoring or
– connect the signals N and N externally (see Section 10.1)
•
Edge-to-edge distance between the edges of the counted pulses.
•
Failure of the encoder power supply.
Frame error
The frame error monitoring for absolute encoders (SSI) cannot be deactivated. It monitors the frame as
follows:
•
Start and stop bit errors
•
Monitoring of the monostable flip-flop period of the connected encoder
Missing pulses (incremental encoder)
An incremental encoder must always supply the same number of increments between two consecutive
zero markers.
The FM 452 checks whether the zero marker of an incremental encoder occurs at the correct encoder
status.
For encoders without zero markers, you must deactivate error pulse monitoring. You must also
deactivate wire break monitoring or connect the zero marker inputs N and N externally.