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United States Patent no]
Fujiwara et al.
[li] Patent Number:  Date of Patent:
 SEQUENCE CONTROL APPARATUS
 Inventors: Katsuhiro Fujiwara; Kazuyoshi
Osako, both of Narashino, Japan
 Assignee: Hitachi, Ltd., Tokyo, Japan
 Appl. No.: 284,341
 Filed: Jul. 17, 1981
 Foreign Application Priority Data
Jul. 18. 19X0 :.1P| Japan 55-97554
 Int. CI. G06F3/00
 U.S. CI 364/200
 Field of Search 364/200 MS File,
 References Cited
U.S. PATENT DOCUMENTS 4,159,516 6/1979 Henrion et al 364/200
"Microprocessors & Microcomputers'". Givone e! al., 1980, p. 282.
Motorola—M6800 Microprocessor Applications Manual pp. 5-12, 5-34, 1975.
Primary Examiner—Eddie P. Chan
Assistant Examiner—Tim A. Wiens
Attorney, Agent, or Firm—Antonelli, Terry & Wands
In a sequence control apparatus using a microprocessor performing its processing of operation in terms of one word as the unit therefor, a change indicating signal from a process condition detecting or measuring instrument connected to an I/O unit is taken into the microprocessor in a form combined with predetermined pattern data. With the resulting composite data, the contents of those bits of an accumulator in the microprocessor which do not correspond to the change indicating signal can be optionally processed.
8 Claims, 5 Drawing Figures
U.S. Patent Feb. 26,1985 Sheet 1 of2 4,502,112
U.S. Patent Feb. 26,1985 Sheet 2 of 2 4,502,112
SEQUENCE CONTROL APPARATUS
BACKGROUND OF THE INVENTION
1. Field of the Invention 5 The present invention relates to a sequence control
apparatus, and more particularly to such an apparatus designed exclusively for sequence control in which the contents of control are determined by a program.
The variety of demands for sequence control appara- 10 tuses have increased with the development of automation. If one relies on electromagnetic relays or logic elements in order to fulfill such demands, the alteration of the contents of a control sequence makes it necessary to rewrite a complicated diagram for wiring on a relay 15 or logic element board and to fabricate the corresponding new board. This results in lowered productivity in factories. Further, the fact that the alteration of the contents of control sequence is associated directly with a change in the contents of the hardware, causes various 20 problems from the aspect of production control.
The contents of sequence control realizing a systematic running of a plant cannot be determined until the specifications of all instruments employed in the plant have been determined and the mutual relation between 25 the instruments has been established. According to the conventional approach, therefore, the specification of the sequence control apparatus is determined in a final stage, followed by the design of the apparatus and the fabrication of the hardware required therefor. Thus, the 30 sequence control apparatus is to bear the brunt of a severe restriction even in the fabrication process.
In view of the above problems, an approach has been proposed by which the hardware of a sequence control apparatus is standardized to allow the fabrication of 35 identical hardwares on a production line of a factory while various requirements from users are settled by software. There has been widely used a programmable sequence control apparatus based on a stored program scheme in which a main part of the hardware is left 40 unchanged for different sequence controls while the alteration of the contents of control operation is effected by modifying a program.
The present invention relates, in particular, to such a programmable sequence control apparatus using the 45 stored program scheme.
2. Description of the Prior Art
A conventional sequence control apparatus of this sort includes as main parts thereof an input unit, an output unit, an operation control unit and a memory 50 unit. The input unit is connected to an instrument (for example, a limit switch) for detecting the condition of a process to be controlled by the sequence controlling apparatus. The output unit is connected to a process controlling instrument (for example, an electromagnetic 55 switch or a solenoid valve) which is controlled by the sequence control apparatus. For example, when a limit switch is activated in response to a change in a certain process, the change indicating signal is applied to the operation control unit of the sequence control apparatus 60 through the input unit, and then collated with a predetermined control program stored in the memory unit to determine a required control action. As a result, a control signal is sent to the output unit so that a solenoid valve is closed. The contents of the sequence control 65 operation to be performed are previously stored in the memory unit in the form of a program. When it is desired to store the program in the memory unit or to
modify the contents of the program, an exclusive unit called a "program input unit" is connected to the memory unit and it is operated in accordance with a sequence chart.
The above-described kind of sequence control apparatus is designed exclusively for use in sequence control and therefore has functions which are intensively prepared to provide the best utilization for sequence control. Most of the instructions forming a program are suited to sequence control. For example, there are employed a STORE instruction, an AND instruction, an OR instruction, an AND/STORE instruction, an OR/STORE instruction, an OUTPUT instruction, and the like. The operation control unit is provided with an accumulator. A change indicating signal resulting from a change in a certain process, for example, the activation of a limit switch, is once entered in the accumulator through the input unit for collation with a predetermined control program stored in the memory unit. The contents of necessary control determined by the control program is once stored into the accumulator and then sent to the output unit as a control signal. The STORE instruction requires taking a change indicating signal from a predetermined process condition detecting instrument into the accumulator while transferring as an intermediate result, the result of the previous operation which has been stored in the accumulator before the taking of the change indicating signal thereinto, to a shift register prepared as a temporary memory unit. The AND instruction requires producing a logical product of the result of the previous operation stored in the accumulator and the change indicating signal newly taken from the predetermined process condition detecting instrument into the accumulator and returning the result of this logical operation to the accumulator to be stored therein. The OR instruction requires producing a logical sum of the result of the previous operation stored in the accumulator and the change indicating signal newly taken from the predetermined process condition detecting instrument into the accumulator and returning the result of this logical operation to the accumulator to be stored therein. Each of the AND instruction and the OR instruction does not act on the shift register serving as the temporary memory unit. The AND/STORE instruction requires producing a logical product of the result of the previous operation stored in the accumulator and the result of operation taken out of the shift register or temporary memory unit through a shifting of the latter and returning the result of this logical operation to the accumulator to be stored therein. The OR/STORE instruction requires producing a logical sum of the result of the previous operation stored in the accumulator and the result of operation taken out of the shift register or temporary memory unit through a shifting of the latter and returning the result of this logical operation to the accumulator to be stored therein. The OUTPUT instruction requires delivering the result of the previous operation stored in the accumulator.
The contents of sequence control determined by the control program is stored, as a sequence program including a proper combination of the above-mentioned instructions, into a memory unit by means of the program input unit.
The recent advance of microprocessors is remarkable and a sequence control apparatus using a microprocessor in its operation control unit has been widely used.