Digital input/output device

Dunn et al. (58) interfaced a DEC PDP 11-10 computer to a DuPont Model 990 thermal analysis system. The BCD-binary converter used a cascade of 15 6 bit BCD-binary ROMs to convert the 4.5-digit BCD output of the Hewlett-Packard Model HP 3430D digital voltmeter to bit binary for input to the DEC DR-11C general input-output device. All software was written in FOCAL, under the RT-11 operating system. 

Peripherals for user input/output card readers (obsolete), card punches (obsolete), line printers (almost obsolete), laser printers, terminals, also called CRT (cathode-ray tubes), speech recognition devices, speech synthesizers, optical scanners, modems (modulators— demodulators, to piggyback digital data onto an acoustical carrier for telephone transmission), IR laser ports, and so on. 

Using the analog and digital devices described above, one can design the on-line communication link, or interface, between the digital computer and the experimental system. Several fundamental considerations must be kept in mind How does the particular computer use, recognize, and interpret information from the outside world How does the computer transmit information What are the computer machine-language instructions available for input/output (I/O) functions ... 

Bus coopling components Signal (analog, digital, impuls input/output Direct digital information from digital field devices... 

Communication with the computer is carried out by input-output (I/O) operations. Typical input devices are keyboard, magnetic tapes and disks, and the signals of an analytical instrument. Output devices are screens, printers, and plotters, as well as tapes and disks. To convert analog information into digital or vice versa, the aforementioned ADCs or DACs are used. 

Input and output operations are similar to memory read and write operations, with the exception that a peripheral I/O port is addressed instead of a memory location. The CPU issues the appropriate input or output command, sends the proper device address, and either receives the data being input or sends the data to be output. Data can be input/output in either parallel or serial form. All data within a digital computer are represented in binary-coded form. A binary data word consists of a group of bits Each bit is either a 1 or a 0. Parallel I/O consists of transferring all bits in the word at the same time, one bit per line. Serial I/O consists of transferring one bit at a time on a single line. Naturally, serial I/O is much slower, but it requires considerably less hardware than does parallel I/O. 

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