Patent GB-1236386-A (GB)
Title: Improvements in the electrical transmission of data between spaced locations
Inventor: WILLIAMSON DAVID THEODORE NELS
IPC: H04L12/403
Filed: 1967-09-15
Abstract: 1,236,386. Programmed control of machine tools. MOLINS MACHINE CO. Ltd. Sept. 13, 1968 [Sept.15, 1967], No.42277/67. Heading G3N. The electrical transmission of data over a pluratity of conductors in a parallel mode between a transmitting and a receiving station is controlled by comparing sent and received signals and initiating transmission of data on identity between the signals through an instruction channel. As shown, a machine-tool complex comprises data-controlled machine tools MT1-MT4 which are serviced with loaded pallets by a transporter T2 from a storage rack 5R. The pallets are loaded with blanks by an operator at a bench OB who subsequently removes finished price-parts or resets partlymachined blanks when a change of attitude of the blank on the pallet is needed. The complex is controlled by a computer EC which optimizes machine tool utilization and communiates with the units by a multi-channel bus CB comprising three channels, an instruction channel IC, a reporting channel RC and an address channel AC. The address channel is sub-divided into a control data line ACD, a control instruction line ACI, and control reporting line ACR; the instruction channel is sub-divided into a control instruction line ICI and a control data line ICD; the reporting channel is sub-divided into a report function line RCF and a report data line RCD. The units of the complex are connected to the bus by link units, which comprise a link unit ECL for the computer EC and identical slave link units MTL1-MTL4, TL1, TL2, OBL for the machine tools, transporters and operator bench respectively. When in use the lines carry multi-digit signals in parallel-mode, each link-unit having an identifying address in four out of eight code. The computer, in sequence, cyclically communicates with each slave unit. A cycle commences with a signal on line ACD from master link unit ECL representing the address of the slave unit, followed after a short delay by a signal on line ACI. The called up slave unit responds by emitting a signal on line ACR and master slave unit ECL now emits a signal on line ACI whereby the slave unit temperarily stores prepared signals on lines ICI, ICD, and acknowledges by a signal on line ACR. A subsequent signal on line ACI from master link unit ECL causes the slave unit to break the link to lines ICI, ICD and acknowledge on line ACR. The master link unit thereupon establishes an internal link between lines RCD, ICD and emits on line ACI a signal causing the slave link unit to carry out the temporarily stored instruction and send its address on line RCD to master link unit ECL which are returned via line ICD. The slave link unit compares the emitted signal on line RCD with that received on line ICD. An equality, signifying no faults on lines ICD, RCD, is notified by the slave link unit to the master link unit on line ACR. A firm communication having been established, any desired instructions required by the computer programme are sent to the slave link unit to initiate desired operations of the complex unit. These instructions are acknowledged and checked. After all further instructions have been sent, the master link unit sends a signal on line ACI to terminate operation of the slave link unit, which acknowledges, if no data is to be sent, on line ACR. The next phase of the cycle is then initiated for the next slave link unit. The sequence of signals on lines ACI, ACR are such that each succeeding linary signal involves the application on removal of voltage on one conductor only, thereby avoiding the appearance of spurious signals during a change.