L9_DISA: Monitor Disabled Coils and Inputs
(Original Document)
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Function Description
The Disabled Discrete Monitor (L9_DISA) monitors disabled states of coils (%Mx) and inputs (%Ix) located in State RAM.
A L9_DISA function allows the ladder diagram of a Quantum or M340 PLC to find and annunciate disable states as they occur. The function logs the quantity and addresses of the disabled coils and inputs into simple tables.
HMI systems and other host devices can be used to make this information available to operators.
If you disable inputs and coils you must ensure to document the user initiated over-ride to be able to restore the normal operating mode of the control system. The L9_DISA function helps to undo user initiated over-rides by alerting programmers and maintenance personnel to the presence of inputs and coils disabled in logic.
WARNING
UNINTENDED EQUIPMENT OPERATION
Use only State RAM addressing (instead of topological addressing), if you want to detect forced bits by using L9_DISA.
L9_DISA does not detect forced coils and inputs (%Ix, %Qx), if forcing has been done by using topological addressing (e.g. %I0.4.1).
Failure to follow these instructions can result in death, serious injury, or equipment damage.
NOTE: Please note that system word 108 (%SW108) contains the total number of forced bits (%I, %Q, %M), even if topological addressing is used.
Representation
Parameters
Input Pin
Name
Data Type
Address Range
Meaning
Top
ENABLE
BOOL
–
ON = enables operation
Node
Node Type
Name
Data Type
Address Range
Meaning
Top
IN/OUT
DCOIL
ANY_ARRAY_UINT
%MW
table with the number and addresses of disabled coils found
Middle
IN/OUT
DINPT
ANY_ARRAY_UINT
%MW
table with the number and addresses of disabled inputs found
Bottom
IN
LENGTH
UINT
1...100
table length (number of words used for the table)
valid range: 1 to 100
NOTE: If LENGTH=1 only the number of disabled inputs is displayed.
Output Pin
Name
Data Type
Address Range
Meaning
Top
DC_FOUND
BOOL
–
ON = disabled coils are found
Middle
DI_FOUND
BOOL
–
ON = disabled inputs are found
Bottom
ACTIVE
BOOL
–
Echoes state of the top input (ENABLE).
Example
The Disabled Discrete Monitor (L9_DISA) can detect and store the addresses of up to 99 coils and 99 discrete inputs.
The quantity of coils and inputs is counted into DCOIL and DINPT in case the number of disables exceeds the table length reserved for storage of disables.
A table length of 10 would actually use 20 holding words, 2 for storing quantities, and 9 each for storing the addresses of disabled coils and disabled inputs.
The search routine of the programming software will locate only the programmed top node and middle node plus its data table as defined by the bottom address.
The following is an example of a possible program:
Address
Value
Meaning
%MW100
3
indicates 3 disabled coils
%MW101
7
coil %M7 is disabled
%MW102
11
coil %M11 is disabled
%MW103
1247
coil %M1247 is disabled
%MW110
12
indicates 12 disabled inputs
%MW111
1
input %I1 is disabled
%MW112
9
input %I9 is disabled
%MW113
15
input %I15 is disabled
%MW114
18
input %I18 is disabled
%MW115
25
input %I25 is disabled
%MW116
293
input %I293 is disabled
%MW117
768
input %I768 is disabled
%MW118
901
input %I901 is disabled
NOTE: The quantity of disabled discrete inputs is indicated as 12, whereas the allocated length for storage is only 9. This would indicate 4 additional disabled inputs exist for which insufficient %MW storage space has been allocated. Since the inputs are listed in ascending numerical order those inputs not listed must be addresses greater than input number %I901 (the last one listed).