F374_DDTR

Redundant instruction

NOTE

This is a redundant instruction. It is replaced by: FP_DETECT_CHANGE

The function detects changes in a value at input s by comparing it with its former value that is stored at output d. If the new input value at s does not coincide with the old value, the function assigns the new value to output d. To signal the change, the system variable sys_bIsCarry is set simultaneously.

Parameters

Input

s (DWORD, DINT, UDINT, DATE, TOD, DT): 32-bit area for detecting data changes

Output

d (DWORD, DINT, UDINT, DATE, TOD, DT): 32-bit area where data of previous execution is stored

Remarks

Instead of using this F instruction, we recommend using the corresponding FP7 instruction: FP_DETECT_CHANGE
The status of the carry flag is updated at each execution of the instruction. Therefore, programs that use the carry flag should utilize it immediately after F374_DDTR is executed.

Error flags

sys_bIsOperationErrorHold (turns to TRUE and remains TRUE)

if the input value at s has changed in comparison to the former value.

sys_bIsOperationErrorNonHold (turns to TRUE for one scan)

if the input value at s has changed in comparison to the former value.