Mask Equal To (MEQ)
This information applies to the CompactLogix 5370, ControlLogix 5570, Compact GuardLogix 5370, GuardLogix 5570, Compact GuardLogix 5380, CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, and GuardLogix 5580 controllers.
The MEQ instruction passes the Source and Compare values through a Mask and compares the results.
Available Languages
Ladder Diagram
Function Block Diagram
Function Block Diagram supports these elements:
FBD Block
FBD Function
TIP:
FBD Function is applicable to CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, Compact GuardLogix 5380, and GuardLogix 5580 controllers only.
Structured Text
This instruction is not available in structured text.
Operands
There are data conversion rules for mixing numeric data types within an instruction. See Data Conversions.
Ladder Diagram
Operand | Data Type CompactLogix 5370, ControlLogix 5570, Compact GuardLogix 5370, and GuardLogix 5570 controllers | Data Type CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, Compact GuardLogix 5380, and GuardLogix 5580 controllers | Format | Description |
|---|---|---|---|---|
Source | SINT INT DINT | SINT INT DINT LINT USINT UINT UDINT ULINT | immediate tag | Value to test against Compare. |
Mask | SINT INT DINT | SINT INT DINT LINT USINT UINT UDINT ULINT | immediate tag | Which bits to block or pass. |
Compare | SINT INT DINT | SINT INT DINT LINT USINT UINT UDINT ULINT | immediate tag | Value to test against Source. |
Function Block Diagram
FBD Block
Operand | Data Type | Format | Description |
|---|---|---|---|
MEQ | FBD_MASK_EQUAL | tag | MEQ structure |
FBD_MASK_EQUAL Structure
Input Members | Data Type | Description |
|---|---|---|
EnableIn | BOOL | Enable input. If false, the instruction does not execute and outputs are not updated.
Default is true. |
Source | DINT | Value to test against Compare. |
Mask | DINT | Defines which bits to block, such as mask. |
Compare | DINT | Value to test against Source. |
Output Members | Data Type | Description |
|---|---|---|
EnableOut | BOOL | Indicates if the instruction executed without fault when it was enabled. |
Dest | BOOL | Set to true when result is true. Cleared to false when result is false. |
FBD Function
TIP:
FBD Function is applicable to CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, Compact GuardLogix 5380, and GuardLogix 5580 controllers only.
Input Operands (Left Pins) | Data Type CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, Compact GuardLogix 5380, and GuardLogix 5580 controllers | Description |
|---|---|---|
Source | SINT INT DINT LINT USINT UINT UDINT ULINT | Value to test against Compare. |
Mask | SINT INT DINT LINT USINT UINT UDINT ULINT | Which bits to block or pass. |
Compare | SINT INT DINT LINT USINT UINT UDINT ULINT | Value to test against Source. |
A SINT or INT tag is converted to a DINT value by zero-fill. | ||
Output Operand (Right Pin) | Data Type | Description |
|---|---|---|
Dest | BOOL | Set to true when result is true. Cleared to false when result is false. |
See FBD Functions.
Operation
A "1" in the mask means the data bit is passed. A "0" in the mask means the data bit is blocked. Typically, the Source, Mask, and Compare values are all the same data type.
If using SINT or INT data type, the instruction fills the upper bits of that value with 0s so that it is the same size as the DINT data type.
Enter an immediate mask value
When entering a mask, the programming software defaults to decimal values. To enter a mask using another format, precede the value with the correct prefix.
Prefix | Description |
|---|---|
16# | hexadecimal, such as 16#0F0F |
8# | octal, such as 8#16 |
2# | binary, such as 2#00110011 |
Affects Math Status Flags
No
Major/Minor Faults
None specific to this instruction. See Index Through Arrays for array-indexing faults.
Execution
Ladder Diagram
Condition/State | Action Taken |
|---|---|
Prescan | N/A |
Rung-condition-in is false | Set Rung-condition-out to Rung-condition-in. |
Rung-condition-in is true | Refer to MEQ Flow Chart (True). If output is true Set Rung-condition-out to true else Clear Rung-condition-out to false |
Postscan | N/A |
Function Block Diagram
FBD Block
Condition/State | Action Taken |
|---|---|
Prescan | N/A |
EnableIn is false | Set EnableOut to EnableIn. |
EnableIn is true | Set EnableOut to EnableIn. Refer to MEQ Flow Chart (True) .If output is true Set Dest to true else Clear Dest to false |
Instruction first run | N/A |
Instruction first scan | N/A |
Postscan | N/A |
FBD Function
TIP:
FBD Function is applicable to CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, Compact GuardLogix 5380, and GuardLogix 5580 controllers only.
Condition/State | Action Taken |
|---|---|
Prescan | N/A |
Normal Scan | Refer to MEQ Flow Chart (True) .If output is true Set Dest to true else Clear Dest to false |
Instruction first run | N/A |
Instruction first scan | N/A |
Postscan | N/A |
MEQ Flow Chart (True)
Examples
Example 1
If the masked value_1 is equal to the masked value_2, set light_1 to true. If the masked value_1 is not equal to the masked value_2, clear light_1 to false.
This example shows that the masked values are equal. A 0 in the mask restrains the instruction from comparing that bit (indicated by an x in the example).
Ladder Diagram
Function Block Diagram
FBD Block
FBD Function
Example 2
If the masked value_1 is equal to the masked value_2, set light_1 to true. If the masked value_1 is not equal to the masked value_2, clear light_1 to false.
This example shows that the masked values are not equal. A 0 in the mask restrains the instruction from comparing that bit (indicated by an x in the example).
Ladder Diagram
Function Block Diagram
FBD Block
FBD Function
Provide Feedback