FEATURES OF LOGIC CONTROL SYSTEMS FOR PHOTO-RECORDING OUTPUT DEVICES FOR ELECTRONIC DIGITAL COMPUTERS

Yu. M. Achkasov, V. A. Beinarovich, Yu. I. Potekhin, L. S. Udut,
A. D. Kozhukhovskii, S. S. Krykin

(Presented by the Sector for Automation of Processes of Oil and Gas Prospecting and Production, Research Institute of Automation and Electromechanics)

Digital computers cannot make use of a large volume of information if they are not equipped with input and output devices. In most modern computers, information input and output are carried out by means of magnetic-tape units or magnetic drums; in small information-processing systems, devices using punched tape or punched cards are often employed.

The external output devices of modern machines usually include a high-speed printer with a speed of up to 1000 lines per minute. Xerographic printing devices, for example the SK-3000 type manufactured by Stromberg-Carlson, and electrostatic printing devices manufactured by Burroughs, have higher speeds—up to 1800 lines per minute with 100 characters per line.

Recent developments in output printing devices make it possible to achieve output speeds of up to 5000 lines per minute. However, the use of printing devices for outputting information when analysis of calculation results is required cannot always be employed. It is often necessary to have information on the results of calculations presented in analog form (transient-process curves, hodographs, trajectories, etc.).

Existing plotters (of the DRP type) are intended mainly for analog computers, and their use together with electronic digital computers requires additional digital-to-analog converters and filtering devices. In addition, they possess all the shortcomings inherent in plotting instruments. Therefore, the creation of high-speed output devices for electronic digital computers, making it possible to obtain information in analog form for subsequent processing or visual observation, is a pressing task. Solving this problem expands the limits of the use of electronic digital computers and simplifies the verification of research results processed by means of electronic digital computers.

At the Scientific Research Institute of Automation and Electromechanics of Tomsk Polytechnic Institute, an output device has been created—a seismic-section plotter (PSR) for BESM-4 and Minsk-22 type electronic digital computers—which makes it possible to obtain seismic sections of the earth’s crust on photographic paper from the results of processing geophysical information on an electronic digital computer. A cathode-ray tube (CRT) is used to record traces on photographic paper.

In the present work, the logic control system (LCS) of the plotter is considered; it provides automatic control of the operation of the “EDC—PSR” system. For this purpose it generates commands:

1. Starting the magnetic-tape storage unit of the electronic digital computer to rewrite the information of the next trace from the magnetic-tape unit into the computer’s RAM.

2. Calling the number code from RAM.

3. Moving and stopping the carriage with the moving CRT, depending on the playback modes.

4. Switching the CRT beam on and off, likewise depending on the playback modes and on the position of the photographic drum.

The seismic signals being reproduced are nonstationary oscillatory processes with frequencies from 5 to 100 Hz and a dynamic range of 42 dB. The signals are recorded by their discrete values, at intervals of 2 msec of real geophysical time, on standard magnetic tape of a BESM-4 or Minsk-22 magnetic-tape unit.

Each signal (geophysical trace) has no more than 2500 discrete values (nine-bit binary numbers).

When reproducing traces on photographic paper, the following conditions must be met: 1) the beginning of the recording of each trace must coincide with the beginning of the preceding one; 2) a time shift of the discrete values of one trace relative to the discrete values of another is inadmissible.

Photographic recording of traces is performed at two scales of real geophysical time: 5 sec—the full trace, and 2.5 sec—half-traces.

The functional diagram of the LCS is shown in Fig. 1.

Here \(D_1\) is the number-call sensor. It generates 3000 pulses per one revolution of the photographic drum.

\(D_2\) and \(D_3\) are sensors of the position of the photographic drum relative to the CRT. Sensor \(D_2\) produces a signal at the moment when the photographic-paper fastening zone (PZP) passes in front of the CRT. On the leading and trailing edges of this signal, the “beginning of PZP” and “end of PZP” pulses are formed by shapers \(\Phi_2\) and \(\Phi_1\), respectively.

Sensor \(D_3\) is put into operation when a half-trace is being recorded and determines the start of reading information from RAM.

RP is the intermediate relay for switching on the electromagnetic clutch.

The logic-control circuit is assembled from standard elements of the “Ural-10” complex.

The rotational speed of the photographic drum is 10 rev/min.

Let us consider the operation of the LCS in the normal mode when recording a full trace on photographic paper. After the digital information of one trace has been rewritten from the magnetic-tape unit into the RAM of the computer, the signal “end of recording in RAM” is sent to the logic-control circuit. It prepares trigger \(T_1\) (Fig. 1). This means that the machine is “ready” to output information. The recording of information on photographic paper begins on the “end of PZP” pulse, which arrives from sensor \(D_2\) through shaper \(\Phi_1\) (see the timing diagram in Fig. 2). By this signal, reading is enabled and the CRT is switched on. Through the coincidence circuit, pulses from sensor \(D_1\) enter the electronic digital computer to call the number code.

On the “beginning of PZP” pulse formed by shaper \(\Phi_2\), recording is stopped, the CRT is blanked, and the signal “start MTU” is sent to the computer from shaper \(\Phi_3\). By this signal the electronic digital computer rewrites the next trace from the magnetic-tape unit. Upon completion of recording the trace, the next signal “end of recording in RAM” is sent to the logic-control circuit. The next trace is recorded in the same way.

The logic-control system provides protection against malfunction that occurs when the “end of recording in RAM” pulse arrives later than the “end of PZP” pulse. In this case, no information is called and no trace is recorded; the electromagnetic clutch for moving the CRT is disconnected, the tube remains blanked, and the photographic drum makes an idle revolution.

In the accelerated mode, recording of either half of a track is provided. In this case the rotation speed of the photodrum is doubled, while the number-calling frequency remains the same, since in this mode the output from sensor \(D_1\) is connected through flip-flop \(T_6\) with the counting input. After the arrival of the pulse “end of recording in RAM,” the signal from sensor \(D_3\) permits the calling of numbers, by which the information is read from RAM. The information itself is recorded on the pulse “end of ZKF”; on the pulse “start of ZKF,” the ELT is inhibited, and the information remaining in RAM is erased when the next track is rewritten. If, during the passage of the ZKF, the machine has not managed to rewrite the track from the NML into RAM, then on the pulse “end of ZKF” the electromagnetic clutch for ELT displacement is switched off. The drum makes an idle revolution. With the arrival of the pulse “start of ZKF”

Fig. 2. Timing diagrams: a) when recording a full trace; b) when recording a half-trace

on the next revolution the electromagnetic clutch is switched on and, upon the “end of ZKF” pulse, the CRT is switched on; recording of the next half-trace takes place.

The logic-control system provides for recording traces in groups of 23 or 24 traces, as well as continuously, depending on the position of the switch on the front panel of the PSR control console.

To count the recorded groups of traces, and also to form 23 (24) “start NML” pulses when recording traces in groups, a group decoder is provided, consisting of five flip-flops with counting inputs. The trace counter counts each trace by the “start of ZKF” pulse (see the timing diagram).

The proposed logic-control system makes it possible to implement automatic operation of the “EDC—output device” systems.

References

1. Yu. M. Achkasov, V. A. Beinarovich, A. D. Kozhukhovsky, L. S. Udut. A logic control system for a seismic-section plotter. Proceedings of the VI Scientific and Technical Conference on Production Automation. Tomsk State University Press, Tomsk, 1969.

2. Geophysical Apparatus. Special Design Bureau of the Ministry of Geology of the USSR, issue 36. Nedra Publishing House, Leningrad, 1968.

3. Digital Recording and Processing of Seismic-Prospecting Information, oil-and-gas geology and geophysics series, VNIIОENG, Moscow, 1968.