Rockwell Automation 1771-PD PID MODULE (+DU) - Manual (Page 87)

Programming
Chapter 3
3Ć44
W61(W68)B10 Integral Term>Integral Term Limit. Rest to 0 the
integral term V I is less than or equal to the integral term limit V I
MAX in word W26(W46). Set to 1 the integral term is greater than
V I MAX. The bit status is reported whether or not integral term
limiting is selected.
W61(W68)B07 Loss of Analog Input. Rest to 0 the analog input
signal from an input device is present and can be found in word
W64(W71). Set to 1 the hardware analog input is less than the
minimum value of +4mA or 1VDC. A loss of hardware analog input
will be detected whether or not a PV value is downloaded from the
PC processor into word W09(W16).
The loss of a hardware analog input will cause the corresponding
loop output to be held at its last value until the input is restored.
However, if the process variable has been downloaded from the PC
processor into word W09(W16), loss of a hardware analog input will
be detected but will not cause the analog output to be held.
NOTE: When downloading PC values from the PC processor when an
input device is not connected, jumper the INPUT (+LEAD) terminal to
the +15VDC terminal to prevent the loss of input bit W61(W68)B07 from
being set.
NOTE: Loss of input detection when analog inputs are configured in
voltage mode requires the use of 10K ohm 1/4 watt resistor. The resistor
must be connected between the INPUT (+LEAD) and (-LEAD) terminals
to ensure loss of input detection for an open or short circuit in one or both
leads of the input device. The module input impedance is thereby reduced
to 10k ohms. A resistor is not required for loss of input detection for
current mode analog inputs.
If either decoupling or cascading is selected and the hardware analog
input to loop 1 is lost, the output for both loops will be held
regardless of the status of the loop 2 inputs.
The loss of a hardware analog input is indicated by bit B07 of loop
status word W61(W68) and bit B02 of the status monitor byte.
W61(W68)B06 Loss of Tieback Input. Reset to 0 indicates that the
tieback input signal is present and can be found in word W66(W73).
Set to 1 indicates that the input is less than the minimum value of
+4mA or +1VDC.