| 摘要 |
<p>A production control system is provided, especially for use in a works environment, in which a microsequencer controlled by a Z80 microcomputer board (MUXC) performs continuous high-speed scanning of a multiplicity of operator input devices (OIDs) located at the work stations of individual human operatives. The microsequencer is essentially a single-level pipelined microprocessor communicating with the OIDs via channels and sub-channels, each OID being connected to a respective sub-channel by a single twisted-pair cable. The cable lines are maintained at 24 volts d.c. to supply power to the OID, and the OID, which has a card-reader for reading bar code on cards or tickets passed through it by the operative, transmits data to its subchannel, and hence the microsequencer, over the same cable by shorting out the two cable lines for short and long pulse periods. The microsequencer checks the validity of each read and responds to the OID to indicate a good read or otherwise - this response is sent in a morse-type code to audio and visual responders in the OID by temporarily reversing the polarity of the same two lines of the communicating cable. The Z80 microcomputer loads microcode into the microsequencer and thereafter supervises the scanning and datareception and checking functions. Good reads are stored in shortterm storage in the MUXC and can be transmitted to up-date the data base of a host minicomputer. Serial link communication between the MUXC and the host computer is via channels incorporating adapters having optical isolating devices to ensure compatibility and satisfactory transmission over distances in a factory environment.</p> |
