M
main routine
A routine in a program configured to execute first when the program runs.
major fault
A controller fault that stops execution in the controller and transitions to Fault mode. Examples of major faults are a loss of a critical I/O module or overtravel on a motion axis.
When you clear a major fault, if the controller keyswitch is in Run mode, you will be asked to confirm the clearing of the faults because the controller will immediately begin running again when the fault is cleared.
Tip: | This clears the major faults and the major fault log (displayed in the Recent Faults area of the dialog). |
In the Safety controller, non-recoverable faults can occur. When a non-recoverable fault occurs in a Safety application, the Safety task will not run again until you re-download the project, or until the Safety components are reinitialized from a Safety signature in the controller.
When a non-recoverable Safety fault exists, you will still be able to edit the standard application. However, you are restricted to editing only those portions of the Safety application that are accessible while in the Safety Locked state.
Whenever a non-recoverable Safety fault exists, or the project is Safety Locked, or a Safety signature exists, or the Safety Status (on the Safety tab of the controller properties) is any value except OK, the Safety application and certain parts of the standard application are not able to be edited online or offline. Once you have cleared the Safety fault, you can download, upload, or go online with the controller.
When a recoverable Safety fault exists, you can edit both standard and Safety applications.
major revision
A functional change to the module. The major revision indicator is updated anytime this
occurs.
mask
A binary value with its bits set to a pattern. The pattern selectively screens out or lets through certain bits, in a data value, to specify the bits to be operated in generating a masking result value.
master clock
A system of 1588 clocks may be segmented into regions separated by boundary clocks. Within each region, there will be a single clock, the master clock, serving as the primary source of time. These master clocks will in turn synchronize to other master clocks and ultimately to the grandmaster clock.
master control relay (MCR)
A mandatory hard-wired relay that can be de-energized by any series-connected emergency stop switch. Whenever the MCR is de-energized, its contacts open to de-energize all application I/O devices.
master control reset (MCR)
A ladder logic instruction used to delimit MCR zones.
master CST
The designated controller with which all other modules, in a single chassis, synchronize their Coordinated System Time (CST) values.
Tip: | Only one controller must be designated as the master CST. |
matching project file
A project file matches the project in a controller if the project file:
- was downloaded to or uploaded from the controller
OR
- is a copy of a project file that matches the project in the controller
If you have a matching project file, you can go online to the target controller by performing an upload merge, which preserves your offline project documentation.
Logix Designer
does not allow you to upload into an existing project file if it does not match. This prevents the accidental loss of your project documentation.media redundancy
Redundancy of a communication network's physical transmission media only. Identical information is transmitted across both media; the receiver has circuitry to select the media with the best transmission quality. If one of the transmission media is seriously degraded or damaged, network communication continues across the other media.
member
An element of a structure that has its own data type and name. Members can also be structures creating nested structure data types.
memory
The electronic storage media, built into a controller, used to hold programs and data.
MESSAGE
A structure data type that contains status and control information for a MSG instruction.
minor fault
A controller fault that does not stop execution in the controller nor transitions to Fault mode. Examples of minor faults are a watchdog triggered on a task or a low battery.
minor revision
A change to a module that does not affect its function or interface. The minor revision
indicator is updated when this occurs.
mnemonic
A term used to represent a complex or lengthy set of information.
modes
Selected methods of operation (for example, Run, Test, or Program mode).
module
A device, typically an I/O device, that communicates with the controller. The controller, a particular 1756-IB16I or a PanelView are all considered modules.
module-defined data type
A structure data type defined by a module when you create it. Tags of these types are created to store input, output, and configuration data for the module.
module-defined tag
A tag defined by a module when you create it. Tags are created to store input, output, and configuration data for the module. See module-defined data type.
module fault
A problem or error in a module of the control system. A fault in a module also causes a connection fault in any controller with a connection to that module.
module reference parameter
A module reference parameter is an InOut parameter of the MODULE data type that points to the Module Object of a hardware module. You can use module reference parameters in both Add-on Instruction logic and program logic. Since the module reference parameter is passed by reference, it can access and modify attributes in a hardware module from an Add-On Instruction.
morph
To change the type of instruction. This is a result of editing the instruction’s mnemonic field. When you edit the mnemonic field, the instruction-type changes.
most significant bit (MSB)
The bit representing the greatest value within a string of bits.
most significant digit (MSD)
The digit representing the greatest value within a string of digits.
motion direct command
A motion command that is sent directly to the controller from the software as a result of a user action. These commands execute without being initiated by a user program.
Motion direct commands can be executed in Program mode, Remote Run mode and while the controller is in Major Fault State.
MOTION_GROUP
A structure data type that contains status and control information for a motion group.
MOTION_INSTRUCTION
A structure data type that contains status and control information for motion instructions (for example, MSO, MAM, and MAS).
motor
A device that converts a form of energy into mechanical energy.
- AC motor- converts (single or multiple phase) alternating electrical current into mechanical energy. It requires not commutation devices such as brushes.
- AC synchronous motor- rotates at a speed proportional to the frequency of the applied AC.
- Brushless servo motor- uses electronic commutation to convert DC into the AC applied directly to the motor, so that brushes are not needed. This type of motor can provide the good stall torque of a DC motor without the problems of mechanical commutation.
- DC motor- converts direct electrical current into mechanical energy. It includes a commutation device, such as a brush.
- DC permanent-magnet motor- uses permanent magnets to produce a magnetic field. It has linear torque-speed characteristics.
- General-purpose motor- has a continuous Class-B rating and design. It is listed and offered in standard ratings with standard operating characteristics and mechanical construction. It is used under unusual service conditions without restriction to a particular application or type of application (NEMA).
- Multispeed motor- can obtain 2, 3, or 4 discrete (fixed) speeds by the selection of various stator-winding configurations. (Induction motor.)
- Servo motor- used in closed-loop positioning control. This type of application usually requires high linearity.
- Special-purpose motor- has special operating characteristics and/or special mechanical construction. It is designed for a particular application and is not a general-purpose or definite-purpose motor (NEMA).
- Stepper motor- allows discrete positioning without feedback. (Specialized DCmotor.)
multicast
A mechanism by which a module can produce data on a network simultaneously received by more than one listener. This term is used to describe a feature of the ControlLogix I/O line. It supports multiple controllers receiving input data from the same I/O module at the same time.
multi-owner
A situation where more than one controller in a multicast I/O configuration is capable of supplying configuration data for the I/O.
Tip: | In the 1756 I/O line, the I/O configuration data in various controllers of the multi-owner configuration must match. |
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