Save counter value
The latch function enables the current counter value to be stored in separate process data, independent of the cycle time. The latch function can be triggered as follows:
- Gate/Latch input: positive/negative edge at the Latch input (Enable latch extern on positive/negative edge)
Index 0x80n0:22 "Enable continuous latch extern" can be used to parameterize whether the function is executed at every parameterized external edge at the latch input or only once after every activation.
Multiple activation of the latch function If several commands are activated simultaneously to save the counter value in the "Latch value" process data (index 0x60n0:12), only the command that is set first is accepted by the terminal.
|
Save counter value via a positive/negative edge at the Latch input (Enable latch extern on positive/negative edge)
- The counter value at the Latch extern input can be saved via:
- Index 0x70n0:02 "Enable latch extern on positive edge" = TRUE
At the first external latch pulse with positive edge the current counter value is stored in index 0x60n0:12 "Latch value". - Index 0x70n0:04 "Enable latch extern on negative edge" = TRUE
At the first external latch pulse with negative edge the current counter value is stored in index 0x60n0:12 "Latch value". - Simultaneous activation of 0x70n0:02 and 0x70n0:04
The current counter value is stored in index 0x60n0:12 "Latch value", at the first external latch pulse, independent of the edge polarity. - Specification whether it is necessary to reactivate the command to save the counter value via:
- "Enable continuous latch extern" Index 0x80n0:22 = FALSE
The following pulses at the Latch extern input have no influence on the latch value in index 0x60n0:12 "Latch value" when the bit in index 0x70n0:02 or 0x70n0:04 is set.
A new counter value can only be written to the Latch input in index 0x60n0:12 "Latch value" if index 0x60n0:02 "Latch extern valid" is FALSE - "Enable continuous latch extern" Index 0x80n0:22 = TRUE
The counter value is written to index 0x60n0:12 "Latch value" at every parameterized edge at the Latch extern input.
There is no need to reactivate index 0x70n0:02 or 0x70n0:04. - Saving of the counter value in index 0x60n0:12 "Latch value" is confirmed via the "Latch extern valid" bit (index 0x60n0:02).
- The status of the Latch extern input can be monitored via index 0x60n2:14 "Status of extern latch".
Activation of gate and latch functions via the same edge at the gate/latch input in two-channel mode 2xAB When the gate function and a latch function is activated via the same edge at the gate/latch input, the latch function is always executed first, after which the counter value is disabled via the gate function. Example: Index 0x80n0:04 "Gate polarity" (1 = "Enable pos. gate") and Index 0x70n0:02 "Enable latch externally on positive edge" =1 With a positive edge at the gate/latch input the current counter value is first stored in index 0x60n0:12 "Latch value". The counter value is then blocked. The same applies to index 0x80n0:04 "Gate polarity" (2 = "Enable neg. gate") and simultaneous activation of index 70x0n0:04 "Enable latch extern on negative edge". |