A standard NASBUS 8″ x 8″ PCB: twelve may be fitted to a system to use all 256 available ports, each board with three parallel input/​output controllers, one counter timer circuit and one universal asynchronous receiver-transmitter. Each board may be fitted only with the options necessary, though later uprates are simple. Boards are supplied with documentation covering all options.

Each device carries two 8-bit read/​write parallel data ports with separate control signals; applications for this type of device include direct interfacing with many digital-to-analogue and analogue convertors, the control of relays or electronic power controllers and uncomplicated EPROM programming.

The use of this device saves complex programming when the system is required to count or time internal or external events; essential for instrumentation, process control and experimental robotics, it permits a higher program speed without sacrificing control.

Supplied with its own crystal clock and monolithic baud rate generator, this device frees the system computer’s serial port to allow simultaneous operation of, for example, a cassette mass storage system and a printer. A V24/​RS232C serial interface is also provided for direct connection to terminals and VDUs.

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