NORD Drivesystems BU0550 - Manual (Page 74)

PLC logic for NORD SK 54xE frequency inverters
74 BU 0550 GB-0813
3.5.8 Recording of rapid events (FB_Capture)
The cycle time of the PLC is 5 ms, under certain circumstances this cycle is too long to capture very fast ex-
ternal events. Via FB Capture it is possible to capture certain physical values on flanks at the FI inputs. The
inputs are monitored in a 1 ms cycle. The values which are saved can later be read by the PLC.
With a positive flank on EXECUTE all inputs are read in and the Capture function is enabled. The FI input
which is to be monitored is selected via the INPUT input. The typ of flank and the behaviour of the module
are selected via EDGE.
EDGE = 0 With the first positive flank, the selected value is saved under OUTPUT1 and DONE1 is set to 1.
The next positive flank saves under OUTPUT2 and DONE2 is set to 1. The FB is then deactivated.
EDGE = 1 Behaviour as under EDGE = 0, with the difference that the negative flank is the trigger.
EDGE = 2 With the first positive flank, the selected value is saved under OUTPUT1 and DONE1 is set to 1.
The next negative flank saves under OUTPUT2 and DONE2 is set to 1. The FB is then deactivated.
EDGE = 3 Behaviour as under EDGE = 2, with the difference that first the negative flank and then the posi-
tive flank is the trigger.
If the input CONTINUOUS is set to 1, then only the settings = and 1 are relevant to EDGE. The FB contin-
ues to run and always saves the last triggering event under OUTPUT1. DONE1 remains active from the first
event. DONE2 and OUTPUT2 are not used.
The BUSY output remains active until both Capture events(DONE1 and DONE2) have occurred.
The function of the module can be ended at any time by a negative flank on EXECUTE. All outputs retain
their values. With a positive flank in EXECUTE first of all, all outputs are deleted.
Table 100 FB_Capture
NOTE
Several instances of this FB may exist in the PLC program. However, only two
instances may be active at the same time!
VAR_INPUT VAR_OUTPUT
Input Explanation Type Output Explanation Type
EXECUTE Execute BOOL DONE1 Value in OUTPUT1 valid BOOL
CONTINUOUS Single execution or continuous
operation BOOL DONE2 Value in OUT valid BOOL
INPUT Input to be monitored
0 = Input 1
- - - -
7 = Input 8 BYTE BUSY FB still waitng for a Capture event BOOL
EDGE Triggering flank BYTE ERROR the FB has an error BOOL
SOURCE Value to be saved
0 = Position in rotations
1 = Actual frequency
2 = Torque BYTE ERRORID Error code INT
OUTPUT1 Value for first Capture event DINT
OUTPUT2 Value for second Capture event DINT
ERRORID Explanation
0 No error
1900h INPUT value range exceeded
1901h EDGE value range exceeded
1902h SOURCE value range exceeded
1903h More than two instances are active