Siemens SIMATIC S5-90U System Manual page 501

S5-90U/S5-95U
Prerequisites for a Synchronization
• 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.
• Traversing path 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.
• 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 16.18 and 16.20a).
• 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 16.19).
The module is not synchronized, if a negative traversing path is recognized after the falling
edge of the reference signal (see figure 16.20b).
The figures 16.18, 16.19 and 16.20a illustrate different possibilities for a reference traversing
path. Figure 16.20b illustrates a reference traversing path, which is terminated without
synchronization:
Reference
signal
Reference pulse
of the sensor
Sync
bit
Figure 16-18. Position of the Reference Point (SYNC Bit=1) within the
Reference
signal
Reference pulse
of the sensor
Sync
bit
Figure 16-19. Position of the Reference Point (SYNC Bit=1) after the Reference Signal
EWA 4NEB 812 6115-02b
Positive direction of traverse
Reference Signal Range
Positive direction of traverse
Function Modules
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