Siemens SIMATIC FM 452 Manual page 87

Address Name
59.0 CNT_DIR
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
63.0 MON_WIRE
63.1 MON_FRAME
63.2 MON_PULSE
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.
FM 452 Electronic Cam Controller
C79000-G7076-C452-04
Type Initial Value
BOOL FALSE
Type Initial Value
Monitoring:
BOOL TRUE 1 = wire break
BOOL TRUE 1 = frame error (must always be 1)
BOOL TRUE 1 = missing pulses
Machine Data and Cam Data
Comment
Count direction:
0 = normal
1 = inverted
Comment
8-19