Abstract: A field apparatus for controlling a controlled element includes a diagnosis unit for diagnosing abnormality of the field apparatus and/or the controlled element and a bidirectional digital communication device to send a digital signal which shows a diagnosis result to outside and to receive a digital signal from outside in order to execute a control of the controlled element. Other predetermined functions are effected based on a command signal in the form of an analog signal received from outside by a analog communications device of the apparatus. Electric power for operation is supplied through a switching means that can switch either a electric power that is supplied by the analog communications device or a electric power that is supplied by the bidirectional digital communication device.

Abstract: A field apparatus (1a) comprises a diagnosis unit (11) diagnosing abnormality of oneself or a controlled element and a bidirectional digital communication means (22) to send a digital signal which shows a diagnosis result to outside and to receive the digital signal from outside in order to execute a control of controlled element and other predetermined functions based on a command signal received by a analog communications means (17) that can receive a analog signal from outside. A electric power for operation is supplied through a switching means (18, 53) that can switch either a electric power that is supplied by the analog communications means (17) or a electric power that is supplied by the bidirectional digital communication mean (22).

Abstract: The present invention is a block oriented control system that allows interoperability between devices made by different manufacturers. A block oriented control system is a system which includes a plurality of field devices incorporating a physical layer, communication stack, and user layer, with the field devices being connected by a transmission medium, such as a bus. The physical layer receives signals from the bus and translates the signals into a message for the communications stack, and receives messages from the communications stack and translates the messages into signals for the bus. The communication stack controls the communications between devices operating in the control system. The user layer is a block oriented approach to the system's control functions, and includes function blocks and system management. The function blocks are standardized encapsulations of control functions, such as analog input or proportional/derivative.

Abstract: For obtaining diagnosis information, as well as in use of digital communication, at low cost with no need for special hardware and software, in a control system of conventional analog input-output type, a positioner executes control of a valve and other predetermined functions based on an analog input signal received through analog communication with an outside controller. It has an arithmetic processing unit for diagnosing abnormality of either or both of the positioner itself and the valve, and an analog diagnosis signal transmitter for transmitting an analog signal (4-20 mA) indicating result of diagnosis. The analog signal has a value of range corresponding to the result of diagnosis.

Abstract: When each access apparatus is to update its own data written in a common memory device, the transmitting unit of each access apparatus transmits the previous data previously written in the memory device and new data to be newly written in the memory device as a pair of data via a bus. Upon receiving the pair of data from the access apparatus, a determination unit in the common memory device determines whether the data stored in a memory coincides with the previous data received from the access apparatus. If these two data coincide with each other, the data in the memory is rewritten into the new data; otherwise, a data update in the memory is rejected.

Abstract: The present invention is a block oriented control system that allows interoperability between devices made by different manufacturers. A block oriented control system is a system which includes a plurality of field devices incorporating a physical layer, communication stack, and user layer, with the field devices being connected by a transmission medium, such as a bus. The physical layer receives signals from the bus and translates the signals into a message for the communications stack, and receives messages from the communications stack and translates the messages into signals for the bus. The communication stack controls the communications between devices operating in the control system. The user layer is a block oriented approach to the system's control functions, and includes function blocks and system management. The function blocks are standardized encapsulations of control functions, such as analog input or proportional/derivative.

Abstract: When each access apparatus is to update its own data written in a common memory device, the transmitting unit of each access apparatus transmits the previous data previously written in the memory device and new data to be newly written in the memory device as a pair of data via a bus. Upon receiving the pair of data from the access apparatus, a determination unit in the common memory device determines whether the data stored in a memory coincides with the previous data received from the access apparatus. If these two data coincide with each other, the data in the memory is rewritten into the new data; otherwise, a data update in the memory is rejected.

Abstract: In order to insure the accuracy of information transmitted over a network, the initiation of the message must be unambiguously identified. In the present invention, the intermessage spacing consists of a series of identical logic signals that exceeds a minimum value distinguishing this interval from a message character. The message character has predefined length, with a start bit position logic signal and a stop bit position logic signal bounding the character that has the same number of predetermined logic signals for every message character. The character has at least one additional non-data bit position that has a first logic signal for the initial character of a message and the complementary logic signal for the remaining characters in the message.

Abstract: A communication system is provided in which a plurality of communication devices communicate with one another over a plurality of transmission lines. One of the communication devices operates as a master station, while the remaining devices are slave stations. The master station periodically transmits transmission line specifying signals which specify or identify which of the transmission lines is to be used by the devices for communicating with one another. The master station, when operating normally, will periodically change the transmission line in use so that each of the plurality of transmission lines is used in turn and for substantially similar periods of time. At such time as any one of the slave stations detects a problem in a transmission line in use, that slave station will transmit an abnormality detected signal.