Siemens SIMATIC S5-100U System Manual page 446

Function Modules
Prerequisites for a Synchronization
1. The reference signal
The sensor for the reference signal is connected to terminals 7 and 8 of the terminal block.
Synchronization is enabled with the leading edge (0 to 1) at terminal 8. If the signal was
already on "1" when the module was switched on, then the reference signal must be turned off
to restart the synchronization.
If the reference signal lies in the normal traversing range, the actual value will be constantly
resynchronized by the reference signal. To prevent the unwanted resynchronizing, you have to
mask out the reference signal after the first reference point approach.
2. The traversing direction after a positive edge of the reference signal
After the reference signal has been reached, the module has to recognize a positive traversing
path (up-counting) while the reference signal is still active (1). This means, you have to input
the reference signal with increasing actual value to synchronize the module.
3. The reference pulse
The reference pulse is generated by the position encoder at least once per revolution.
• The first reference pulse that the module recognizes after a leading edge of the reference
signal synchronizes the module (see figures 15.17 and 15.19a).
• If the reference signal changes from "1" to "0" before the reference pulse is reached, the
module is only synchronized if a positive traversing path is recognized after the falling edge
of the reference signal (see figure 15.18).
The module is not synchronized, if a negative traversing path is recognized after the falling
edge of the reference signal (see figure 15.19b).
The figures 15.17, 15.18 and 15.19a illustrate different possibilities for a reference traversing
path. Figure 15.19b illustrates a reference traversing path, which is terminated without
synchronization:
Reference
signal
Reference pulse
of the sensor
Sync. bit
Figure 15-17. Position of the Reference Point (SYNC Bit 0 --> 1) within the Reference
Signal Range
Reference
signal
Reference pulse
of the sensor
Sync. bit
Figure 15-18. Position of the Reference Point (SYNC Bit 0 --> 1) after the Reference Signal
15-32
Positive direction of traverse
Positive direction of traverse
S5-100U
EWA 4NEB 812 6120-02b