Abstract: A coordinated system time is established for spatially separated components of an industrial control system using synchronizing messages transmitted over a communication link between those parts. Precisely coordinated actions may be obtained at separated components by the use of a time conditional command received by those components prior to a time of execution the command instructing the component to execute the command only when at execution time in the future has been reached. The coordinated system time may be used to time stamp received triggering events for use in coordinating subsequent actions based on those triggering events.

Abstract: A decompiler works with a compiler for an industrial controller having a user modifiable instruction table to contain code fragments necessary to compile particular instructions. During compilation, the instructions are replaced with the code fragments. Thus new instructions recognizable by the compiler may be added simply by editing this instruction table. The decompiler identifies a portion of the compiled new instructions by reference to the same instruction table used by the compiler thus maintaining compatibility with the compiler.

Abstract: Driving circuitry for a switch matrix provides a reset voltage to all rows of the matrix in between scans to recharge switch capacitance. Column detection circuitry is disabled in between scans so that column driving circuitry may also `reset` the charge on capacitors reducing the scan time and/or allowing a greater number of switch elements, element size, or EMI suppressing capacitances. Pull-up resistors are supplemented or eliminated through the use of active current sourcing and sinking for the drivers.

Abstract: An industrial controller having a number of addressable I/O modules, employs an I/O map table linking software addresses used for developing the control program to actual physical addresses of the I/O modules on a network. By employing software addresses for connection points to the control process, the program may be developed independent of the topology of the network connecting the processor to the I/O modules and changes in that topology may be made without affecting the control program, but simply by changing the I/O map table. A single change in the I/O map table re-connects an I/O module for all references in the control program.

Abstract: A contactor for use in controlling electrical motors may include a mechanical stop engaging the armature of the contactor and having an eyebar receiving one or more shackles of padlocks to prevent closure of the contactor contacts despite the application of an actuation current. An auxiliary switch may disconnect the coil of the contactor when the stop is positioned to lock the contactor providing additional resistance to actuation of the contactor 10.

Abstract: A task executed on a multi-tasking industrial controller is employed to monitor data exchanged between a control program (executed as a second task on the industrial controller) and the controlled process. The monitoring task, which may be invoked on a periodic basis, reads designated data, compares it to its last value and if it changes, stores the value in a buffer. A separate program reads this buffer and displays relevant information to the user minimizing degradation in the performance of the control program and eliminating the possibility of corruption of the control program as would be required for the introduction of special memory trapping instructions into the control program.

Abstract: Multiple processing units connected along a communication link to form an industrial controller may arrange for efficient block transfer of data by isochronous methods by forwarding to a data producer a connection message including the desired data structure having the variables necessary to be transmitted in a predefined order. Upon receipt of the data structure, the data producer may program itself to collect the data into the structure and forward the data on a periodic basis dictated by the connection message to the data consumer. Changes in the data structure may thus be accommodated efficiently in a manner that is invisible to the user.

Abstract: A compiler for an industrial controller uses a user modifiable instruction table to contain code fragments necessary to compile particular instructions. During compilation, the instructions are replaced with the code fragments. Thus new instructions recognizable by the compiler may be added simply by editing this instruction table. Multiple instructions having the same name are resolved through a best match of operand types which examines the possible data loss in conversion of operand types to select a particular one of the instructions.

Abstract: An industrial controller executing a graphical language employs a comparator circuit for monitoring the address locations of memory used to store the control program and its data. A cursor positioned on a graphics representation of the program is used to identify a particular graphical element to be monitored and the address of the starting instruction for that element is loaded into the comparator. An interrupt generated by the comparator causes the generation of a histogram listing the particular rungs name and the times at which it has been executed, useful for verifying and monitoring the operation of a control program. A snapshot of data values used by the element of the program at the time of its execution may also be stored to verify the condition under which the element executes.

Abstract: A program for partitioning a centrally developed industrial control program into component that may be download to distributed devices for execution and control of an industrial process divides elements of the control program into spatially linked elements which are associated with physical devices that have defined locations and spatially independent elements that have no defined location within the control structure. The spatially linked elements are grouped together according to their proximity and the spatially independent elements are assigned to those groupings so as to minimize communications between the various links. The cost of the grouping, the band width of the signals and the capabilities of the modules are also considered.

Abstract: A method of editing a real-time control program as it controls equipment is provided in which the editing occurs in a second area of memory and integrated into the pre-existing program by means of conditional jump instructions concatenated to that edited material. The pre-existing program is uninterrupted by the editing process except for a change of single instructions which do not affect the results of the execution but redirect the execution thread of that control program to be conditionally connected to the edited material. This single writing of single instructions, which do not affect execution results, precludes the possibility of the controller executing partially edited programs. The jump instructions are conditional on a test edit pointer to allow instantaneous implementation of the edits and a simple return to unedited instructions simply by changing the state of the flag.

Abstract: A communication network for an industrial control system permits multiple masters and complex network topologies by transmitting data as packets through paths of nodes on the networks. The packets containing data are preceded by an OPEN message which pre-configured each node with the necessary information to process the stream of succeeding packets in an efficient manner and thus to reduce the necessary overhead in the transmission of each data packet. Each node receiving the OPEN message evaluates its resources and if those resources are insufficient to reliably handle the indicated packets, a message is returned to the originating node indicating that a connection cannot be formed.

Abstract: A co-processor interface allows both a general processor and a relay ladder processor to make repeated calls to each other in the execution of subroutines. A register transfer instruction detected by the relay ladder processor triggers a suspension of the general processor. Return of control to the general processor is accomplished at the same time a register value is provided to the general processor that the general processor uses to reinitialize its program counter. For most single level transfers of control, a single transition instruction between the general processor to the relay ladder processor is sufficient to perform a call.

Abstract: Multiple motion controllers for controlling servo motors are connected by a digital communications link so that controlled axes of the motion controllers may be slaved together regardless of their physical proximity. A given controller broadcasts position or command signals on the communications link in response to a request report message from any other controller. A second request report message may stop the broadcasting to conserve link capacity. Time shifting implicit in the link messages is corrected by estimating the velocity of the master axis and extrapolating the position to the local axes' time of updating.

Abstract: An input to a complex multi-input process, such as injection molding, is optimized to produce a target output from that process through the use of a neural network trained to that process. A trial input is forward-propagated through the neural network and the output of the network compared to the target output. The difference is back-propagated through the network to determine an input error value in the network. This error value is used to correct the trial input. This correction process is repeated until the trial input produces the target output to within a predetermined degree of accuracy.

Abstract: A method of providing a standard coordinated time throughout spatially separated functional modules of an industrial controller employs a module operating as a time master which transmits a coordinated time to various dependent modules through communication modules. The dependent modules have local clocks which are synchronized to the coordinated time value by adjusting their clock frequency according to the difference between local time provided by that clock and the coordinated time value. This gradual correction prevents lost count values and disruption to the control process. The most and least significant bits of the time value may be transmitted at separate rates to reduce link traffic.

Abstract: The present invention provides for electronic braking of DC brushless motors by developing a feedback signal based on the back EMF of the motor. This feedback signal is used to provide a signal to the motor permitting current flow from the motor into the controller of a controlled level to slow the motor down. Reliance on the back EMF of the motor eliminates the need for a commutation signal when an emergency stop is required.

Abstract: A multitasking industrial controller for real-time control of machinery and the like permits the use of both periodic and event driven tasks by establishing a hierarchy of both task types in the form of priorities that resolve conflicts between events of the same and different types. The unpredictability of the event driven tasks on scheduling of tasks is addressed by watchdog time values assigned to each task which confirm timely execution of the task in practice despite the risk of preemption by other tasks. Flexible software definition of event driven tasks is made possible by delegating the detection of the events to input/output modules executing independently of the processor executing the operating system.

Abstract: A method of operating an industrial control system converts relay ladder logic programs into flow type programs expressed as `logical gates` connected with `wires` representing variables. This formulation is converted to an efficient code structure in which changes in state of the variables are evaluated and only changes are propagated in evaluating program outputs. The net effect is many steps of evaluation in the control program are avoided during real-time operation of the program connected to controlled equipment.

Abstract: A multi-tasking industrial controller for real-time control of machinery and the like permits the use of both periodic and event driven tasks by establishing a hierarchy of both task types in the form of priorities that resolve conflicts between events of the same and different types. Each task may access a common "global" memory area to communicate information and timing with other tasks and so as to coordinate the overall industrial control process. Trouble-shooting of the task software is made possible by a hardware address monitor which may be programmed to identify access of a particular memory location or range by any task and to record information about the particular task causing that global memory access.