ABB ret650 - Principle of Operation; Design

14.3.3 Principle of operation
Limit counter (L4UFCNT) counts the number of positive and/or negative flanks on
the binary input signal depending on the function settings. L4UFCNT also checks if
the accumulated value is equal or greater than any of its four settable limits. The four
limit outputs will be activated relatively on reach of each limit and remain activated
until the reset of the function. Moreover, the content of L4UFCNT is stored in flash
memory and will not be lost at an auxiliary power interruption.
14.3.3.1 Design
Figure
198 illustrates the general logic diagram of the function.
BLOCK
CountType
INPUT
RESET
ERROR
OVERFLOW
LIMIT1 … 4
CounterLimit1...4
MaxValue
OnMaxValue
InitialValue
VALUE
Operation
Counter
Overflow
Detection
Limit
Check
Error
Detection
IEC12000625_1_en.vsd
IEC12000625 V1 EN
Figure 198: Logic diagram
The counter can be initialized to count from a settable non-zero value after reset of the
function. The function has also a maximum counted value check. The three
possibilities after reaching the maximum counted value are:
• Stops counting and activates a steady overflow indication for the next count
• Rolls over to zero and activates a steady overflow indication for the next count
• Rolls over to zero and activates a pulsed overflow indication for the next count
The pulsed overflow output lasts up to the first count after rolling over to zero, as
illustrated in figure
199.
Section 14 1MRK 504 135-UEN A
Monitoring
442
Technical manual