The Laboratory Interface

Acorn System Laboratory Interface PanelAcorn System Laboratory Interface Main Board

"The Laboratory Interface provides 16 optically isolated connections each of which may function as input or output to the computer system. The opto-isolators and an INS 8154 integrated circuit are amongst the components carried on a standard Eurocard (100 x 160mm) which plugs on to the Acorn computer bus. A remote circuit board with 16 power drivers and LED indicators may be connected by up to 25 metres of 40 way flat ribbon cable to the Eurocard.

The remote circuit board has 16 connections each of which is set to input or output using a switch. In its output mode each connection can drive loads drawing current at up to 3 amperes each from the remote supply voltage which may be in the range 6 to 48v. A catching diode on each output allows inductive loads to be used. In input mode each connection is driven by contact closures to the remote supply common. An LED indicates the state of each connection in input or output mode.

The remote supply voltage is optically isolated from the Acorn system on the interface Eurocard giving the computer immunity to electrical noise generated by the load switching. Noise produced by other equipment at the remote station is also isolated and ground loop problems encountered in the laboratory environment are eliminated. The remote supply can be different to the computer 0 volt line by as much as 48V peak.

Acorn's ONLIBASIC may be used to configure the 16 input/output ports of the INS 8254 such that they match the modes set by the 16 switches at the remote station. Inputs are then read and outputs are then driven by the program. The program may be synchronised to real time using interrupts which are generated by circuitry on the interface Eurocard with a periodic time of 10 milliseconds."

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